Transmission Flush, When and when not to flush transmission

How a Transmission Flush Works

A transmission flush procedure is generally performed using equipment that either runs off the transmission pump or has its own pump built into the machine. The machines are connected to the transmission cooler lines, and while the old fluid is pumped out the new fluid is delivered at the same quantity and time. Sometimes there is a cleaning solvent that is forced back into the transmission removing deposits of old transmission fluid from parts and components or the technician performing the fush may run a solvent through the vehicles transmission before performing the flush. The cooling lines, cooler, converter and other parts are all thoroughly cleaned. One of the benefits of this procedure is that all of the transmission fluid is removed and replaced. This is different from a fluid change in which only some of the fluid is replaced. A simple fluid change cannot remove all of the built up deposits that accumulate over time as is done during a flush. Also, some of the fluid is usually stored in the torque converter potentially contaminating the new fluid that is put in. What is the point of that?

Transmission Flush Good or Bad?

I constantly hear consumer, customers and technicians debate as to whether transmission flush procedures can be harmful to a vehicle and is a transmission flush good or bad for your automobile. While many mechanics and experts agree that having a clean transmission will extend the life of a transmission, it is thought by some that the flushing procedure may not be the best way to achieve a clean transmission. One common thought is that the process, which forces liquid back into the transmission in the opposite way of the normal fluid flow, could potentially damage components or block tight passageways. When fluid is forcefully pushed back into the transmission, chunks of debris can be dislodged and possibly block narrow channels or one-way valves. When new fluid is put back in, these blockages can inhibit the normal flow of fluid through the transmission causing lubrication issues. Nonetheless, many car manufacturers and dealerships contend that these procedures are not harmful at all and help revitalize auto transmissions. MDH Motors does not use a reverse flush machine and over the thirteen years of being in the automotive repair industry I still yet to have seen a machine that flushes the fluid in reverse. Most machines just pump the new fluid in through the transmsiion cooler lines while containing the old fluid in a separate tank. The best transmission flush operation procedure is to:

  1. Perform the transmission flush
  2. Remove the pan and change the transmission filter
  3. Doing the flush in this order while help prevent the possibility of contaminates going through your transmission and potentially causing a problem by, let’s say hanging up a valve in the valve body.

    Checking your transmission fluid

    In the past every vehicle had a second dipstick, other that the engine oil dipstick, which was used for checking the level of the ATF. For vehicles that are still equipped with such, checking the ATF is very easy. Most cars require that the engine be running with the transmission in park. Some require that the transmission be in neutral. Honda trucks and cars with automatics require that the engine be off. If you are not sure what your vehicle requires, you can sometimes find directions on the dipstick itself. If that doesn’t work then consult the owner’s manual or Contact Me and I will be happy to give you some factory procedures.

    Many new cars do not have dipsticks. On these vehicles the fluid must be checked by climbing underneath the car and removing some kind of plug from the side of the transmission in order to see the fluid level. Some of these newer cars will still have the dipstick tube but no dipstick in it. On top of the tube you will find a plug that says in order to check the fluid level you have to take to take the car to the dealership service department. Once there, the technicians can check it with a special tool that looks just like a dipstick. This seems silly and it probably is. The reason for no dipstick is that the car builders want you to believe that you don’t need to check or maintain the fluid. Many of them actually say that the fluid they use is good for the life of the vehicle. This is not exactly true but with modern synthetic fluids, the fluid is at least good for the warranty period and that’s good enough for them. Some cars have a sensor in the transmission that will monitor fluid, and the level can be checked via the information computer located in the instrument cluster. The level is between the marks, then that is satisfactory, and no more fluid is required. If fluid needs to be added then usually it must be poured down the dipstick tube. These dipstick tubes that double as a filler tube are usually wide enough to put the end of a funnel into them. If the dipstick tube is too narrow to fit a normal sized funnel into the end of it, then there is likely a filler plug somewhere else.

    Most cars also require that the engine and transmission be warmed up in order to get the most accurate reading. The reason for this is that ATF expands quite a bit as it warms up. One might believe the fluid level to be low when in reality the fluid is just cold. Many manufacturers put separate marks on the dipstick that are used if the fluid is cold, but what if the fluid is somewhere between cold and warm? This is why it’s just best to check it with the fluid warmed up. The goal when adding or checking fluid is to make sure that the fluid level is between the two are found on the dipstick. If the level is below the lower mark then some fluid must be added, but if besides looking at the level the condition of the fluid can also be examined. If the fluid contains very tiny black particles that rub off on your oil rag or paper towel this is normal, but can it can indicate that the fluid needs to be serviced. These small black particles are bits of clutch pack material that are suspended in the fluid. This is a sign of normal wear and tear but if the particles become excessive, or if the particles are metallic looking; this could indicate some major problems. The last thing you can do that can help determine fluid condition is give it a sniff. Worn out fluid will have a definite burnt smell to it and fluid from a transmission that has completely failed smells downright disgusting.

    Is a Transmission Flush Necessary?

    Ultimately it is wise to consult the manufacturer owner’s manual and follow the guidelines outlined within. If the manufacturer recommends a transmission flush, it is probably advisable to have the service performed. However, it is true that not all manufacturers recommend this service at frequent intervals. It is not uncommon for flushes to be performed only every 100,000 miles. There are two main type of transmission flush machines and I will explain them below.

    Pump inlet flush machine:

    The first type of transmission flush machine I will explain attaches to the pump intake after the pan and filter is removed. This machine only supplies fresh new fluid to the pump intake and as the fluid passes through the transmission it dumps out to a collection tray and never goes back through for a second pass. All of the old fluid and crud is GONE and replace with fresh new fluid. After the service a new filter is installed, the pan replaced and then it is topped off with new fluid to the proper level on the dipstick. This process takes a total of 20 quarts of fluid to flush out 15 quarts of old fluid, replaces the fluid, and gives the mechanic the opportunity to look in the pan for anything unusual that would indicate a pending failure. Everyone should have this type of service done every 30,000 miles, but definitely before your truck goes out of warranty. By looking in the pan you may get an indication that you are about to have transmission trouble that might show up right after you get out of warranty.I will tell you that this type a flush does take more effort and makes more of a mess, costs a little more, but I think it is worth it. The extra charge will be for 1 hour labor and additional parts and fluid.

    Cooler line flush machine:

    The second type of flush machine connects into the transmission cooler lines. BG makes this kind and here is how it works. This type of transmission flush machine is more common in quick lube places where low level lube techs can operate the machine without any problems. They don’t have to operate any electronics or remove the transmission pan. They simply hook up the cooler line and start the vehicle. The other type of flush machines require you to maintain pump pressure and know the correct transmission cooler line flow. The line going from the transmission to the transmission cooler is disconnected and connected to the machine line in. The line out from the machine carrying new fluid is connected to the line going to the cooler. There is a chamber on the machine that has a diaphragm in it. The top part of the chamber above the diaphragm is filled with new fluid. The engine is started which turns the torque converter and the input shaft on the transmission. The input shaft turns the transmission pump and it makes hydraulic pressure. This causes fluid to flow through the cooler line. As fluid leaves the cooler line it enters the chamber on the flush machine. As the old fluid side of the diaphragm fills it pushes the diaphragm up and forces new fresh fluid into the transmission. After a while the old fluid is collected in the machine and it is replaced by new fluid. Now the transmission has been flushed. Really pretty simple. As you can see the machine cause no pressure and all fluid transfer is done by the transmissions own pump.

    Here is what I do not like about this type of machine. When the fluid leaves the transmission pump it passes to two different pressure regulators. One regulator supplies fluid at one pressure to the transmission itself that operates the pistons and controls gear shifting. The other is supplies the torque converter and the transmission cooler. So you can see that all the fluid leaving the pump does not go to the cooler. A bunch of it is cycled through the transmission and dumped back to the pan without going through the cooler. This type of flush machine does not remove all the old fluid, but it continuously dilutes it down with new fluid. It never really removes all of the old fluid, but is far superior to just drain and fill.

    The other thing I do not like about this type of flush is that they sell the supposed benefit that they do not have to drop the pan and change the filter like that is a benefit. Dropping the pan is very important. Looking in the pan is a fantastic diagnostic tool that can tell you if something is going wrong in your transmission. Now let’s say some crud is flushed out of the transmission with this flush method. Where does it go? It can go into the pan, and then sucked up into the filter that may clog the filter causing the pump to starve for fluid and a pressure loss. On the engine the filter is after the pump and if the filter gets clogged there is a bypass valve that opens and oil bypass the clogged filter so the engine is still supplied with oil. Unlike the engine oil pump and filter the filter is on the intake side of the pump. If it gets clogged, that is it, it is clogged and stuff does not get lubricated and the clutches do not get enough clamping pressure and they slip and burn up. In just a fraction of a second you just bought a new transmission if the filter clogs.

    When not to flush your transmission

    Before draining or flushing you should pull the dip stick and look at the fluid. If it is dark, burnt smelling, and you see little flakes or speck in it, DO NOT FLUSH IT. The fluid and transmission possibly has hard part damage, but the transmission just has not figured out it should die yet. If you flush a transmission in this condition it could fail right away. Real strange, but that is what seems to happen. If your transmission is in this condition just drive it while you save for a replacement transmission. There is no way of telling when it will fail. It might be today, next week, or next year, but it is doomed.

    The goal here is to flush the transmission BEFORE the fluid gets contaminated. What you are taking out should look like what you are putting in. Do not wait for a color or smell change. Most manufacturers calls for transmission fluid change at 30,000 mile intervals. The industry standard is two years or 24,000 miles whichever comes first. It is your vehicle, you decide what is best for you.

MDH Motors logo

About Martin Hand

ASE Certified L1 Advanced Mastertech. Martin Hand has 13 years experience in Asian and European Import Auto Repair. Specializing in electrical diagnosis, engine performance, AT/MT transmission repair/rebuild. Martin is also pursuing a degree in Computers Science & Web Programming starting at Portland Community College while he plans to transfer to OIT. Certified in Java application level programming, experienced with other languages such as PHP, Ruby, JavaScript and future plans of automotive diagnostic software development. Please feel free to Ask a Mechanic if you have not received a response for your comment within 72 hours, thank you.


  • Stan says:

    I have a 2000 Camry. It had a loose transmission pan causing it to lose ATF to the point that it wouldn’t drive forward, but it would go in reverse. I fixed the problem, changed the filter and pan gasket, filled up the transmission and now it doesn’t have reverse, but wants to drive forward in neutral and the drive gears. When shifter is put in reverse, it acts like park. I checked the linkage and the neutral safety switch and they all work and point to the correct positions. When the engine is off, but the key is on, and the shifter is in neutral, it will roll just like it should, and it will start the engine, but when the engine is started, it acts like its in drive and will go forward. Any thoughts?

  • mjw83 says:

    I have a 1998 jeep grand Cherokee that had popped radiator 2 times in a week then head gasket replacement directly after. I drove for about 50 miles then tranny started slipping until up to temp then no gears at all. Has roughly 160000 miles and do not think any transmission service ever done. I drained and in bottom of pan was light brown fluid with some grey sludge. No metal shavings found. Could this be from a clogged filter as Lucas treatment was used and fluid thick. Now no gears at all. Any thoughts or advice would be greatly appreciated

  • Jimmy says:

    Also was told bands may be worn and was wondering if they could be tightened or not?Had a computer put on it n it didn’t show any codes and the check engine light is not on.Some say new fluid n filter will help n others say it will make it worse?Please help

    • Martin Hand says:

      At this point it’s not going to hurt, I would be ready to repair the transmission though because of the high mileage. I’m not sure about an external adjustable band either.

  • Jimmy says:

    2003 ford explorer with 203,000 miles with a sealed shutters between 30-50 mph .I have done some hauling also wondering if dumping the pan n changing the filter but not flushing will help or hurt it.Ive put 100,000 miles on it n don’t know if it has ever been serviced.Thanks

    • Mike says:

      My wife had a 2002 Explorer that did the same thing. Finally one day, the thing stopped wanting to shift at normal times and would shift when you let off the gas, very hard. It shuttered for about a year or so. Pretty much, that was the tell tell sign of the tranny failing. Also, if I’m not mistaken, there is no pan to let down. Keep driving it till it quits then get rid of it. New tranny for that thing isn’t work the cost.

  • Tom Parker says:

    I have a 1993 Ford f250 it shifts hard from 1st to 2nd and check engine light is on what could be the problem the check engine light will occasionally go off and then it shifts just fine and when it comes back on it shifts hard from 1st to 2nd again

  • marcus says:

    I recently purchased a 2003 dodge dakota 4 wheel drive with 105000 miles. I do not know if the previous owner flushed the transmission. I was thinking to have this done soon. Is this adequate? The fluid does not smell burnt and does not have dark specs in it. Thanks for the help.

    • James says:

      With the amount of miles you have it wouldn’t be a bad thing to do a flush, but don’t take it to a shop. You can easily do it yourself for a cheaper price. Go to Wally-World and get 15 qts of the cheapest ATF +4 or go an auto store if they have a sale (around $4). Disconnect your transmission cooler lines. You might need quick disconnect tools to get the lines off. I recommend cutting the quick disconnect end off after removing them; they tend to leak after a while. Using 3/8 transmission hoses and 3/4 CTB clamps, add a splice (double ended barb) to pressure to drain into a container. The pressure side is usually on the passenger side. Prep 9 qts of ATF +4 to pour into the transmission from the dipstick. Start the engine, put it in neutral, and start pouring the 9 qts. Once no more ATF is coming out of the pressure line, shut the truck off quickly. Attach the transmission cooler line to radiator. Add an in-line magnetic filter on the return side. Make sure all the added cooler line hoses are the right length. Drain the pan and drop it. Change the filter, clean out the pan, and clean the areas that gasket touches. Install a new gasket with High Tack coated on both sides. You can reuse the old gasket only if it is the molded one with a metal core and it is not torn. Put the pan on and torque it down to specs. Add 4 qts of ATF. Start the truck and put it into neutral. Check your levels and only add to the half way mark. Wait until it is warmed up, and more ATF until it is slightly below max. Take it for a test drive and check your levels afterwards.

      • Martin Hand says:

        I would try to prevent running the transmission empty though. Fill the transmission while vehicle is pumping out old fluid. ATF will pump out faster than you can fill so periodically shut it off to prevent it from running dry.

  • Booker Jones says:

    I have a 2000 Honda civic,while driving it just revs up like it’s in neutral ,if I stop and let it sit for a few minutes it starts back to driving normal. It has a trouble code p1705,which is the trans range sensor, I’ve changed the fluid twice and it still does it. Do you think it’s just the sensor?

  • Michelle says:

    I have a 2006 Mazda 3 Automatic 2.3l 5-Speed.. I recently have been having trouble with the transmission. I was suggested the idea to do a transmission fluid flush, which I did but the problems seem to have gotten worse. The car abruptly shakes when shifted in reverse, the shifting wont go above 3rd gear which causes over-revving. I heard that it may be a bad idea to have done the flush since the new fluids are thinner. Have I ruined my transmission?

  • Kevin says:

    2005 4runner v8 sports edition. No dip stick. Has 143k. No driving or running issues. Going to be towing a few time a year. Have had all the other fluids serviced. From what I’m seeing it’s very complicated to do a franny service. I want to drop the pan and change the filter. Dealer said no filter to change just a screen which would involved labor to take apart further after the pan is deopped. Any thoughts or personal experiences on v8 4runners?

  • Kamal says:

    I have 2007 Nissan Sentra with 84,000 miles on it. The recommended maintenance for transmission oil change is at60,000 miles but was not done. Is it too late to get the transmission oil changed and am I doomed so better to wait, or shall I get it changed ASAP?
    Also, shall I opt for pump or instead flush of the oil?
    Thanks for your help on this

  • Marcus Tibesar says:

    We have a 2000 Buick century and had the transmission fluid changed several months ago. After the change the transmission shifted hard in 2nd and 3rd gears when hot. When the transmission is cold it shifts fine.

    Then we took it back to the same dealer and they changed the transmission fluid AND this time replaced the filter. The car transmission then shifted great (for about three weeks).

    Now it has returned to shifting hard when hot.

    What should we do please?

    • Martin Hand says:

      Time for transmission repair, depending on the mileage it’s possible that there is a problem in the valve body which can be corrected without removal of the transmission.

  • Gabriella says:

    power clean 2000 transmission flush to sell
    I closed the shop express lube automotive, and I want to sell the machine power transmission flush clean 2000 in good condition, if there is anyone interested can contact me via email or (702) 736 4242. Ask for Gabriella

  • Matthew says:

    I just had a new radiator installed in my car. I noticed that my transmission fluid and my coolant was mixing inside the coolant tank and it was a very thick mix like heavy brown creamy fudge. How soon should I get a flush? Also, my torque converter is making a humming sound, why is that?

  • Alex says:

    I have a 2003 Buick Park Avenue Base with 113,000. When pressing the gas to add speed while going in a steady one it gives me 3-5 seconds delay and then it jumps up a little to add the speed. Could that be that I need a transmission flush?

  • Jack says:

    Great article. I have a 2003 V6 Camry. No performance problems at 101000 miles. Took it for an oil change. Transmission fluid looks a little dark but no particles in it. They’re suggesting a transmission flush. Any thoughts or suggestions? Earlier this year, I took it in for annual servicing and the dealer made no mention of transmission issues. Thanks.

  • gage vaughn says:

    i have a 2002 ford f150 4×4 with 7700 package with 4r100 transmission in it. it used to be a old Florida game and wild life truck, I believe the dealership I purchased it from put 4r70 transmission fluid instead of 4r100. when I start it up runs great cold, as soon as the tranny warms up it shift gears hard. any thoughts?

    • Martin Hand says:

      I doubt the fluid is causing the hard shifts but I could be wrong. Most likely there is something in the valve body causing the harsh clutch engagements when hot. You could always add a friction modifier to the fluid to make it compatible.

      • gage vaughn says:

        cool, also it started blinking overdrive, and the p1744 code is coming up today. which that code goes for more than just TCC, I really think it may be shifting solenoids or the tcc solenoids.

        • Martin Hand says:

          Sounds to me like a control problem in the valve body or the solenoids could be the cause but you really need to follow the diagnostic trouble tree for each code, from there you’ll find that usually one failure will set multiple codes. Are you in the Portland area? If so let me know and i can diagnosis it for you.

  • Will says:

    I have a 1998 Buick Regal GS with 109k on it. The vehicle shifts fine under normal driving, but when I try to accelerate hard I hear a grinding noise and the vehicle shifts hard, even causing some wheel spin during the first shift. I had the filter and gasket changed and changed fluid but have not done a flush for fear of further damaging the transmission. I’ve had a couple suggestions and things I’ve found online including a pressure control solenoid or valve and the torque converter. I was just wondering if you had any ideas. When checked before the trans service, the fluid was slightly discolored but not overly so. This only seems to happen at lower speeds too (under 40), it seems to accelerate and shift fine at highway speeds and by accelerating hard I mean 3/4 throttle or more.

    • Martin Hand says:

      I wouldn’t just replace the pressure control solenoid, first you need to check your line pressures under a heavy load. If the pressures are normal then most likely it’s a mechanical problem and the transmission would need removed otherwise the valve body is serviceable on the vehicle.

  • Dave says:

    Thanks for a great article, very well written.

    I have a 2002 Toyota Camry V6 which I *think* has torque convertor lock-up issues when warm. At 45mph, when applying a light right foot to maintain the speed, a judder can be felt. This does not manifest under heavy acceleration through 40-50mph, or when decelerating/braking through 50-40mph.

    The vibration also occurs when accelerating from stationary if not enough right foot is used. So if a tiny amount of right foot is applied, just enough to move the vehicle, it will judder.

    I have read online that this may be cured, albeit temporarily, by dropping out the transmission fluid, flushing the transmission and refilling with manufacturer’s specification fluid. Would you agree with this?

    I appreciate your time in replying.

    • Martin Hand says:

      Sounds to me like your experiencing a torque converter clutch shudder. Yes, replacing the fluid or adding a friction modifier could fix the problem. There could also be a problem with the TCC control circuit or the converter clutch could be burned up.

  • Lina Barroni says:

    I have a 2007 Ford Escape and I bought a used car from a popular car lot in my city 2 years ago,my vehicle now has 150,800 miles and it’s taking a little bit longer to speed up down the highways should I get anything done to the fluid?

  • Gina says:

    Hi Martin,

    Thank you for putting together such a clear and informative article.

    I drive a 2005 Nissan Altima with 186K miles on it – lately, when I put it into drive it doesn’t do anything for several seconds and then jolts itself into drive. Sometimes it takes so long I have to put it into 1st or 2nd (it’s an automatic transmission, not manual) so that it will move, and then I will put it back into Drive.

    Seems from your article that I should not have a transmission flush – but should I still have them check the transmission fluid level? What *can* I do? Or am I doomed?

    Thanks so much.

    • Martin Hand says:

      Yes I would have the fluid level checked. Sounds like the transmission has a delayed engagement which could be caused by a low fluid level.

      • Gina says:

        Thanks, Martin! I will make sure to have that done.

        Another question for you – my husband drives a 2004 BMW 330i, 215K miles – supposedly this car does not need the transmission fluid serviced. But lately, his transmission is also slow to kick into drive by just a few seconds…same answer? Have the fluid level checked?

        • Martin Hand says:

          If the transmission is having a delayed engagement then monitor it, if it is getting worse overtime then the next step would be to remove the transmission pan and inspect. Possible the filter could be restricted.

    • Sean says:

      I am having the same exact issue. 190K with a honda accord. Could you let me know if fluid level ends up being the cause of the jolting/slipping? A few months ago, I added StopSlip to my transmission fluid and it cured the problem temporarily. It’s now back to struggling going into drive, unless I put it in neutral followed by drive.


      • Martin Hand says:

        A lot of the Honda AT transmissions have problems with the filter plugging up. The filter is non-serviceable, the transmission has to be removed and disassembled in order to replace it.

    • Martin Hand says:

      I would have the transmission fluid level checked, you could also have a partially plugged filter. Your losing or have low line pressure causing a delayed engagement. Very possible your going to need transmission repairs soon.

  • Bmw Pete says:

    I have a 2013 Bmw e53 x5 still under warranty,also have a 2002 Bmw e53 x5 it’s not under any warranty but I kept up on all the maintenance and repairs having no problem with the transmission.
    I now have 200,000 miles on the vehicle ,I was thinking about changing the transmission fluid a drain with a new filter, not a full flush but the green tag on the transmission say life time fluid which I know nothing last forever, should I do a flush.

    • Martin Hand says:

      I agree with you that nothing last forever but the manufacturer has engineered that transmission to where is doesn’t need serviced. I think I would trust it, you’ve already made it 200,000 miles.

    • Martin Hand says:

      Your right, nothing lasts forever. That transmission is designed to not have the fluid serviced though, I would trust the engineers. It has made it 200,000K already, pretty good…

  • Beverly Kennedy Hatfield says:

    I am seeking advice on flushing Trans on 2011 YUKON DENALI! My husband is opposed to flushing unless all fluid is removed! ie dropping pan, draining, changing filter and replacing ALL fluid! Most places i’ve contacted says they only replace 7 quarts! How can that be effective if some of old fluid is still in there? Does that no defeat the purpose of clean / preventative flushing?

  • Scott B says:

    I have a 1999 Jeep Grand Cherokee with a 45RFE transmission. It has around 130k on it. It has been hard shifting after it warms up and when i accelerate hard. Just recently I was heading up to the mountains when the check engine light came on and the vehicle went into limp mode. It gave me the code p1734 which is the 2nd clutch pressure switch fault. A couple days later I started the vehicle and the check engine light went off but still have the normal hard shift. The transmission oil is slightly dark so I know it should be changed. Should I get the transmission flushed or just do a normal oil and filter change and drop the pan to see if anything is going on?

    • Martin Hand says:

      I would remove the pan, inspect then change the filter. Clear codes and drive it. If problem reoccurs look into diagnosing the pressure switch fault. After you get the problem fixed then think about performing a transmission flush to completely exchange the fluid.

  • Cassandra says:

    I have a 02 Buick rendezvous. I have no reverse.I got my transmission fluid changed but it didn’t help. Any suggestions

    • Martin Hand says:

      Dirty transmission fluid will not cause no reverse. Change the transmission fluid as a preventative maintenance only. Your going to need transmission repair.

  • Zach N says:

    I have a 2005 Infinity G35 sedan with 86k miles on it. It runs fine but I feel that sometimes it shifts a little late. I bought it at 62k miles and have not flushed the transmission. I am getting mixed messages about whether I should flush it or not. Thank you for this informative article!

    • Martin Hand says:

      Wouldn’t be too worried about the late shift. I don’t know how severe it is though so I can’t say for sure. I would follow the factory recommendations at this point. A transmission flush will most likely not effect your symptoms either.

  • Danny Hedrick says:

    I just purchased a 1971 International 1110 w/345 v8. When I got it it would get to 2nd gear and struggle to change to 3rd until you let off then it would change. I let it sit for about 2 weeks and now it changes from 1st to 2nd with no problem but does not want to go to 3rd. I purchased a new filter and fluid. Should I go ahead and change it and see what happens or go to the shop with it?

  • John Jenkins says:

    Just noticed you are in Portland. Okay. I see you are Asian and European specialist. But I hope you can help me here. I have a 1992 Ford F150 4×4. I have a shudder that starts about 25-26mph and is that way until about 35-37mph. It goes way mostly but really you can still feel it if you are on to it. Is this a transmission, torque converter, engine issue??? I just recently did have the motor tuned. Motor seems smooth. Please help.

    • Martin Hand says:

      At those low speeds, I doubt a torque converter would cause this. Sounds to me like you getting a shudder on the 1-2 upshift or the 2-3 upshift. TCC doesn’t come on until higher speeds.

  • Paul David says:

    Hello, I just purchased a used 2004 Dodge Sprinter with a Mercedes Turbo Diesel engine 215K miles. The van runs and shifts with no problem. I took it to a dealer for a transmission flush and he cautioned that it may do some damage because of the age of the vehicle and the fluid looked/smelled bad. Again, all seems well for now but what can I do to extend the transmission life? (it is a “lifetime” sealed transmission).

    • Martin Hand says:

      If the transmission is a lifetime sealed unit then I would just drive it. These transmissions are engineered to not be serviced and you would be taking an unnecessary risk by performing a transmission flush.

  • Tommy says:

    I have a 2000 Accord coupe ex. What’s the best way to check my transmission fluid? If the transmission fluid get low can I just top if off with new fluid or I have to flush it all out and fill in all new fluid?….

    • Martin Hand says:

      There is a dipstick coming out of the transmission, check with engine off at operating temperature. The fill plug is a 17mm hex on top of the transmission. You can fill it if it’s low, doesn’t need to be completely exchanged.

  • Christine McDonald says:

    I bought an older Honda Accord 2009 and it already had 90,000
    I have no idea if it has ever had a transmission flush..
    Should I do one now?

  • james says:

    Hey Martin,
    My Toyota Aurion Prodigy 2007 has 164 000 on the clock. After the 150k service the automatic transmission started slipping changing from 3rd to 4th and only cold start up. I took it to my mechanic to do a transmission flush which he advised against after sighting the black thick gluey consistency of the fluid. So what would you recommend I do?

    • Martin Hand says:

      I never recommend a transmission service if the transmission is having problems. Transmission flush is for preventative maintenance only, unfortunately you’re going to need transmission repairs at this point.

  • antonio dixon says:

    I have a 2010 ford fusion I’ve never flushed the transmission I’ve only changed the oil now the fluid it’s kind of dark red it jerks sometimes will a flush fix this? Or should I change fluid and filter?

  • Anup says:

    I drove a 2011 Nissan Sentra with 62,100 miles. Is a transmission flush necessary at this point?

  • AJ Reese says:

    I have a 2013 Toyota Corolla with Automatic transmission. Just passed 70k miles and transmission bumps into every gear when accelerating onto the freeway. Do you think it’s time for a flush or just drain and fill? My transmission calls for “WS” fluid but I’ve read a lot of other branded fluids are compatible or interchangeable with WS fluid. What is your suggestion Martin? Also, I’m about to drive from California to Maryland. Need your advice quick.

  • marc stern says:

    2009 murcury mariner premier v6 has 73,000 miles with no transmission issues at this point should i get flushed or just fluid exchange?

  • Erica franceschi says:

    Sorry- I meant 2012 Kia Soul!

  • Erica franceschi says:

    I have a 2022 Kia Soul with 64k. I have never had the transmission fluid changed. It is a bad idea to do it at this mileage

  • Carrie says:

    I have a 2006 Chevy Malibu Maxx Lt 192,792 miles. From the records I can find on the car it had a flush at 65,000 miles (dealer). The person I bough it from claimed that they had the flush done when I followed up with the shop to get it done once more they said they had no records of my car ever getting a flush. I got the car with 160,000 miles on it (It was cheap and I needed a car for school so I didn’t do the best research I was desperate for a car). Now I am having issues with it being delayed when I stop it not going forward right away, hard shifts when I go from reverse to drive, and at times it pulls backwards when I am accelerating at times. I have seen two mechanics and they both have differing opinions. At 180,000 miles I had a used engine put in the car since the other engine had a knocked rod. The one mechanic is adamant that I flush the transmission the other says not to mess with it. Who should I listen too?

  • Rileu says:

    I have a 2005 automati ford Mustang with 120,000 miles on it. I had an issue for a fews months where the stick was harder to move forward or backward. It eventually loosened up and I havent had a problem since. Would you advise against a flush?

  • E.W. says:

    error codes: PO740 Torque Converter Clutch Circuit Open, PO753 Shift solenoid A Electrical, PO758 Shift solenoid B Electrical, PO785 Shift timing solenoid
    What should I do?

  • E.W. says:

    97 Chevy Blazer with mileage 222K, service engine light came on yesterday driving 70mph on freeway, the 3100 rpm was high, didn’t seem to shift into OverDrive. Today Overdrive works, but service engine light is still on. I drained the transmission fluid, put in new filter, new gasket serviced August 2014 mileage 205K. Should I flush the transmission or just drain & refill with new fluid again like it was serviced before? My cousin (a mechanic) said not to flush transmission because of the age & mileage of the vehichle, he thinks it will make things worse. Which is why I didn’t have it flushed last year, just drain & refill with new fluid.

  • Misty says:

    I have a 2003 Buick Rendezvous, 227k miles.
    Shes been having problems shifting gears for the past 9 months or so, and just recently started making a loud buzzing sound while moving/being driven. The sounds pitch increases and decreases with the speed.

    She also has been experiencing obnoxious, grinding, hiccups anytime ill try to accelerate the slightest bit too fast from a complete stop, like at a stop sign.
    I honestly have no idea when her transmission was last maintenanced, this car was passed down to me from my grandma about 2.5 yrs ago and i dont do much upkeep other than oil changes and making sure the main fluids arent low.
    Based on ur article I feel like I should start looking for a new car, but I’d still greatly appreciate your opinion on the matter. Thank you :)

    • Martin Hand says:

      I would have a complete inspection done on the vehicle to get an idea of the condition it’s in and from there decide if it’s worth the money for transmission repair or to just buy another vehicle.

  • Fraser says:

    I have a 1992 GMC 2500 4×4 with a 4L80 transmission. I was planning to do a “home flush” by removing the cooler line and running the truck to pump the fluid out a few quarts at a time, refilling the same amount into the dipstick tube.

    Is this effective on this model transmission?

    • Martin Hand says:

      Yes, you’re doing the same thing as the flush machine would do but just make sure not to run the transmission empty, your better off keeping it overfilled while pumping out old fluid then correct the level when your done flushing.

  • Barb says:

    I have a 2008 Lincoln navigator with 95000 miles. Have not noticed any problems and can’t see in the owners manual to change the fluid. Doesn’t have a dipstick to check it. Some people have told me to flush it and others say not. Is there a recommendation you have for this vehicle?

  • Josh l says:

    I have owned a 96 Hyundai excel gx for 1 year now and recently it has been struggling to engage Overdrive when I hit the button on the highways and also won’t release the key from ignition unless holding the gear lever hard up in park when turned off. From what I’ve read this sounds like something I should check before going and getting a flush.
    PS the Car is past due for a general service.
    196000 kms on the clock.
    Would you possibly be able to advise please?

  • Sunny says:

    I recently purchased a BMW 325i with 66K miles…i keep getting different opinions from indy shops. Some state i should just service my tranmission while others are stating to get a flush as part of my next service to avoid any futher problems. What should i do? Please advise

  • Jesse D says:

    I just bought a 2002 Mazda b3000 with 196k miles on it from my father. It has doesn’t have any problems. It was in bad need of new transmission fluid so I was going to do a flush and put amsoil or royal purple in it to get the longest life I could out of the tranny I could. I decided to do a oil change before I tried a flush to make sure everything was ok with the transmission. The oil was very dark with very little amounts of metals at the bottom of the drain pain, not much in my opinion and very little specks, no chunks. I would very much like the do a flush now but I don’t want to take a working tranny and make it fail. What would you suggest? The oil from the dipstick is now brown not pink.

  • Li says:

    mr.Martin Hand,
    I got a 2011 ford crown Victoria p71 two months ago,the odometer show 180000km,the transmission fluid color light pink,no burnt smell,shift very normal ,went to a CAA recommanded garage,was told :if you do not have any shifting problem,do not touch the ATF.but for me,still want to drop the pan and replace the filter,replace the OEM Mercon LV to AMSoil Signature Series Fuel-Efficient Synthetic Automatic Transmission Fluid.
    is it a good idea?

  • Michael says:

    i have a 93 jeep Cherokee with aw4 transmission. It recently ended up under water during a off-road excursion, and the transmission fluid has water in it and is pink and foamy, has 200k miles, with no transmission problems. I preform a regular filter and fluid change every 12000 to 15000 miles, would it be safe to flush it?

  • casey says:

    98 Honda accord. Gears sound like a wind up toy when shifting from dead stop to full go. Sometimes kicks from the back a little like it’s stuck. Rpms jump up to 4k. Any ideas

    • Martin Hand says:

      Very common to have a restricted or plugged filter on those transmission. Unfortunately the transmission will need removed to service the filter and at that point might as well do a rebuild.

  • Robert says:

    I have a 2004 Dodge Intrepid SE with 88,000 miles on it and sometimes when it downshifts, I hear a light knock and then it gets stuck in 1st. I have to turn it off and back on for it to go awa . Should I get a flush or drain and fill?

  • Peter says:

    I have a 2004 Dodge Grand Caravan with 211 000 kms on it. I replaced the transmission about 1.5 years ago. I just brought it to the dealer for a regular maintenance check and was told I should have a transmission flush. It’s the most expensive item on the menu and it sounded like an up-sell to me more than anything. I haven’t been experiencing any problems with the van. I called my mechanic usual mechanic who is 400 kms from where I live now and he told me that they never recommend a tranny flush to vehicles over 100 000 kms because it messes with the on-board electronic system and will start setting off false problem lights.

    Any comments would be appreciated.

  • roderick says:

    I have a 06 Lincoln zephyr. Had an incident on the the highway where I couldn’t get out of 2nd or 3rd gear. I pulled over and seen a little smoke coming from the hood. Checked the fluid and it was brownish. Got back on the highway with no problems since. Should I do a drain and refill or flush? Also, is the transmission filter serviceable , if so, should I changed that also?

  • Tez says:

    I have a 2005 Acura TL 230,000 miles and I noticed that when I’m put in drive it doesn’t all ways respond when pressing the gas. First gear responds but after second or RPM are real high and I have to cut the car off to make it drive again. Vsa lights flashes before and the car went in limp mode before the above happened. No I’m concerned about the tranny. I was hoping this would be an easy fix but its unknown as of now. I have no check engine lights as well. What should I do?

  • Azizi says:

    Transmission is stalling in my 2000 es300 lexus 141900 miles it feel like uts not going in to gear n ill wait then it will can u tell me whats wrong

  • Kanedog says:

    My 2007 Chevy Tahoe LT has 85,000 miles and last week I noticed it was starting to have slippage while going into second gear. It’s intermittent but I can tell that it’s starting to get a little worse. The CEL is not on, there are some very fine metal shaving in the oil, the oil is a little brownish in color. I took my truck to jiffy lube today and they recommended a transmission flush. What would you recommend? Please Help!

    Thanks in advance!

  • john says:

    Great article and explanation on Transmission Flush. I am on the fence to go in to have my 1998 contour flushed.The CD4E automatic transmission stared experiencing slippage in overdrive and then problem progressed into 3rd gear as well. There’s was a burnt smell to the fluid. Tried replacing the fluid and adding Lucas nonslip additive. This did help in 3rd gear but still noted in overdrive above 100km/hr.

    Some articles indicate it could be clogged pump filter. Have you heard of this issue and could a cleaning of the filter and an inline flush cure this slippage problem?

  • Coad says:

    2003 Baja drives great but, when at a stop light or other stop, the engine vibrates big time. It doesn’t do it while driving, only while stopped, sometimes in Park as well. Its not the engine/transmission mounts and a trans flush which the dealer recommended, didn’t fix it. any ideas?

  • Joseph Somma says:

    I purchased a 2001 Jeep Cherokee two years ago with 124000 miles on it. I nor have 150000 miles on it I was thinking of having the transmission flushed some people are saying to leave it alone it’s running well. Would you recommend I have it done.

    • Martin Hand says:

      On any vehicle with high mileage I would first ask if your have transmission shifting problems, if no then you should service the transmission. I would definitely remove the pan and change filter on top of a complete flush. When you remove the pan look for excessive brass, aluminum, steel or friction material and that can give you an idea of what’s going on, okay.

  • Kenney Johnson says:

    I have a 1999 Chevy Silverado 1500 front wheel drive/six cylinder with 160,000 miles the question I have is I bout this vehicle about a year ago and checked the transmission fluid at the time of the purchase and it seemed ok now it’s starting to grind and pull forward when in gear but stopped would a flush solve this issu? Looking for some sound advice can you help me out

    • Martin Hand says:

      No, I don’t ever recommend a transmission flush when your having transmission performance problems. That vehicle has a 4L60E I believe, there common for the sun gears to break.

      • Anonymous says:

        Clutch packs shatter after awhile happem to my 98 suburban twice within 80000 miles of having it rebuilt

  • CMansfield85 says:

    My transmission shifts into gears but I hear the same noise that a steering wheel makes when you need power steering fluid. It also won’t leave out of 1st gear. What could that be?

    • Martin Hand says:

      Sound like the transmission pump is making noise, same exact concept as a power steering pump just a bigger pump. Make, model or vehicle type would be helpful, thanks.

  • Robert Santos says:

    This is one of the better, explanations and recommendations I have seen regarding transmission flushes. However, your recommendation to not flush a transmission if, “the fluid smells burnt or there are lots of particles” visible in the fluid. Your reason being that your experience has been the transmission often times immediately breaks down and the flush is for not.
    Many automotive engineers cannot understand this theory. They do not understand how changing very old, very dirty fluid can in any way harm a transmission, especially if you remove the pan and change the filter and diligently clean the pan, with a follow up filter cleaning and pan oil change after two or three thousand miles.

    • Martin Hand says:

      I see your point. I always tell my customers that their best service option is to do and flush and remove the pan to clean it out then change the filter. I never recommend a flush if there experiencing transmission problems.

  • Boyce Sr. says:

    Just wanted to tell you that after searching for half an hour looking for some Trans Flush answers I ended up on your site and was VERY pleased. You answered most of my questions in terms I could understand. You never mentioned price letting me believe what you were telling me was for MY benefit rather than yours. All in all a very pleasant and worthwhile time spent.
    Thank you from Las Vegas!!

  • Jim S says:

    I’m trying to keep My 1995 156,000 Bronco On the road Its a one owner so I know its history pretty well and since cold weather set in, I am finding Start up and Go capability is lessoned, over the last few weeks I often hop in Warm it up “breifly” ie: enough to let the Motor oil get around… But usually Not for 30 minutes either I noticed I can drive out and get to say the grocery store which is less then a mile, and no reverse, seems like you pull up to back in a parking spot and The engine stalls, starts and No problem…backs in and everything is fine…. Last ni ght was Cold (getting Very cold over the next couple days) sub zero… and I left my drive got 70 feet down the road and it stalled in drive Loss of power put the 4 ways on, started it back up and sat for 15 and as The vehicle warmed up I began moving the slowly selector from Drive to Neutral.. to neutral.. to drive and after a bit all was good again…. Like everyone these days I would LIKE to keep the vehicle since It Physically fits me well and of course I am on a ixed Income… (I would consider replacing the the Trans you know? Way Cheaper then 50,000 g which keep me from Eating… Thanks for your Thoughts……

    • Martin Hand says:

      I believe that vehicle has an AODE or an AOD (the E is for electronic) transmission. These transmissions are common for valve body control issues. The valve bores wear causing fluid pressure blow by. I’m not sure if you repair AT transmissions but if you look up Sonnaxx they make o-ring end plug kits to fix this problem. Find out what type of transmission for sure and do a little research. You will be surprised on what you find when you know what transmission model your working with. Good Luck!

  • DebLein says:

    Thanks! This is exactly what I was looking for, especially the last section.

    I’m driving a 2001 Chrysler Town and Country that I found on the way to the junk yard for free. Changed out the radiator and water pump and turned it into a wee minivan camper to travel around to all the National Parks while I telecommute. I have driven it for 20,000 miles having gone from Shenadoah Valley, to the Everglades and now at Guadalupe Mtns. On the way to Guadalupe from Big Bend, my check engine light dinged at me, but I was traveling at about 65 mph with the closest town 50 miles out with no other occasion for believing anything was wrong.

    Once I stopped off at Van Horn, I checked the codes and got P1684 and P0700. Battery and transmission related. I have actually felt hiccups in the transmission down in the Everglades between 1st & 2nd. I had Walmart check the fluid when they changed out the oil and they said it all looked good. So I have continued on simply accelerating between 1st & 2nd at a more rapid pace to avoid the “hiccup” feel. (Denial is so helpful!)

    Well, four-wheelin’ (with only a 2wd!) in Big Bend probably didn’t help matters as I was mostly in 1st and 2nd. I have noticed a burn smell but my fluids are all good, though I do have to fill my radiator every once in a while (plus my temps are good). But my tranny fluid doesn’t look so good now, though it is at the right level. I’m at 205,000 miles right now (and I think it got a new transmission back in 2009 at 100k, if I remember what the fellow said).

    I was just thinking I should get the transmission flushed, when I saw your last section. This does seems to be the last leg of this old fellow! I’m hoping for the “year” option you list, or at least, get me to Phoenix!

  • wendy duerst says:

    i’m a manager of a small shop and i need some help i did a transmission service on a 2006 Hyundai Santa Fe and when it come in it was 3 qt. over full i told the customer and he told me to service it . i asked him if it had ever been done before and he told me yes 142000 miles on it and now it will not move after +60.Miles of leaving my shop. fluid is full and the rear end is locked up i don’t thank this could have caused this but i don’t know was told that the trans went out and put a strain the rear end please wright me back thank you

    • Martin Hand says:

      I highly doubt it could cause the problem your explaining. I would assume that the transmission or differential already had an existing problem. Did you remove the pan for the service (if it has a removable pan) and replace the filter? Always a good idea to do this along with a flush. This way you can inspect for excessive metal or friction material in the pan.

  • […] 30 Post(s) Thanks: 31 Thanked 10 Times in 10 Posts iTrader Score: 0 reviews FWIW….…-transmission/ 1999 Camry 3.0 319,000+ miles engine and tranny are original. Timing belt has at least […]

  • daniel says:

    i have a 2000 saturn the gentlman at pep boys suggested ihave the dip stick transmission flush and the the other way ?

    • Martin Hand says:

      I don’t believe the dip stick style transmission flush to be a good service. You just keep mixing clean fluid with old fluid and a lot of transmission fluid is wasted also.

  • don says:

    91 bmw 535i transmission flush now I have no reverse what happened what should I do

    • Martin Hand says:

      I would remove the pan and check if there is evidence of hard part damage (metal or clutch material in the pan). This will give you a better idea of whats going on. You can also perform line pressure tests to help diagnosis this type of problem.

  • rico riley says:

    Hey guys I have read your articular and I have a 93 Toyota Supra my transmission fluid looks lightly brown do you think I should change the fluid and what is the best way to change.Also I heard that people say when you change your fluid you will start having problems my transmission is shifting fine it is just the color of it thanks.

    • Martin Hand says:

      I would perform a complete transmission flush and remove the pan to change the filter (may just be a screen you can clean out). This would be the best service you could perform.

  • mogan says:

    Dear Sir, I have a 1996 Peugeot 405 sri, the problem is water has entered the gearbox due to a faulty Transmission oil heat exchanger which has now been replaced, however the oil though having been drained via the drain plug remains contaminated. How can I flush the oil, is it safe do so. Your advise is much appreciated,

    • Martin Hand says:

      Those transmissions cannot be flushed because you need the cooler lines to pump in/out the ATF. A lot of German models do it backwards this way. Just perform a drain/fill then drive and repeat until the fluid looks good.

  • […] start slipping. i cant find anything right off the back but a quick google search brought me here Transmission Flush, When and when not to flush transmission | MDH MOTORS read the last section. __________________ my 06 scion tc 06 scion tc- injen CAI- exhaust- […]

    • michael says:

      I have a 2012 kia soul,it has 48000 miles.time for transmission service,dealer says it has no transmission filter so it will need to be flushed.does this sound right?

      • Martin Hand says:

        Yes, the Honda transmissions are that way also. This is why it is even more important to keep clean fluid in your transmission. There is a filter but it is not serviceable.

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