By on May 28, 2012


Kurt writes:

Dear Sajeev,

I’m writing about if/when/how to change the transmission fluid in modern automobiles. It’s been my experience when changing the fluid on a vehicle with > 100,000 miles and original tranny, the odds of trans problems within 5,000 miles rise dramatically. The consensus on the interwebs is this was true for older cars, but not necessarily modern vehicles using synthetic fluid. First my history…I’m only listing the cars where I actually changed the fluid. 89 Suburu GL – Fluid Changed at 120,000, total trans failure at 125k. 94 Chevy S10 blazer, trans fluid change at 115k, trans failure at 123k. Current: 2006 Honda Odyssey – Trans Fluid Change at 95K, Torque Converter starting to go out at 100K (yeah, I know this is a weak spot on this vehicle regardless) – wondering if I should change out the rest of the fluid before having someone look at the torque converter?. Additionally what to do about my 2003 Chevy Trailblazer LS (2wd) …..145k, original transmission, original owner, no trans fluid changes ever. The quick lube joint says fluid color is off – looks good enough to me though. I’d like to keep the truck a few more years due to the blood sweat and tears already invested in repairs.

I’ve read that Trans Fluid power flushes can cause more harm than good, and a standard fluid change only swaps a % of the fluid – normally needing 3 of those to get a full fluid swap. Add the twist of certain vehicles needing “special” fluid such as Hondas and it’s hard to say if my failures are due to improper technique by improperly trained quick lube employees, improper fluid, or if changing the fluid isn’t really needed! I always say “I’ll change the trans fluid when the trans fails”. I’m a mild wrench head, some blacked fingernails to prove it ….if my setup allowed it I’d love to change my own fluid – no one cares as much as the owner. However I stopped changing my own fluids after an Exxon Valdez-like accident on my driveway. Any advice on this topic?

Sajeev answers:

Wow, you totally have good luck with transmission fluid changes!  Why not go for a fourth time and see where lady luck takes you?

Or not.

And that’s the big problem: usage of the word “or.” Because, during hindsight analysis, realizing that your ATF-replacement-cum-gearbox-implosion led to a lot of “or” conversations in your CSI-like TV show analysis of the culprit.  Maybe there was nothing left of the clutch’s friction material when the old fluid went in the drain pan.  Or someone put in the wrong fluid.  Or it wasn’t enough fluid.  Or too much.  Or some combination of all the previous “or” statements.

Fun, huh? So in your case…

With your driving conditions, track record on transmission failures AND knowledge of the pitfalls associated with these fluid changes in mind…would you do this a fourth time?  I suspect that no matter the machine, your climate, driving style and ATF changing schedule makes this a bad idea.  Don’t do it.


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40 Comments on “Piston Slap: Damned if you do…...”

  • avatar

    Why on earth is this the case? It defies logic. My mech/tech advised against a change too. Is it possible to do a change with a conditioner/additive that would avoid these weird failures? Should the bands be adjusted at the same time. I just don’t get it.

  • avatar

    It’s a lie that changing the fluid can do more harm than good, ‘dislodging the crud’ which holds it together.

    Your problem isn’t that you changed the fluid and then your transmission failed shortly afterward; your problem is that you waited far too long to bother changing it. It’s akin to doing bypass surgery on a 90-year-old obese smoker.

    I try to change ATF every 25-30k miles. On my 01 Elantra (acquired at 138k miles), I changed the fluid immediately, and then again at 175k miles; it’s still going strong.

    • 0 avatar

      …..Your problem isn’t that you changed the fluid and then your transmission failed shortly afterward; your problem is that you waited far too long to bother changing it…..

      I’m with you on this. I had the same kind of situation when I picked up a Reliant with nearly 100K on the clock. The fluid looked ok, but the lube shop said it was off color, and without a service history, they suggested a change. Interesting to note the service bill had a stamp on it that said “Service Not Recommended” which of course I did not see until the work was finished. The car was scrapped at 253K with a working trans and the same fluid. All my cars now get regular changes, with me doing the work.

    • 0 avatar


  • avatar

    My main beef is that car manufacturers deliberately make it difficult to change tranny fluid. Is it that damn hard to put a drain plug in the tranny case? I know you have to drop the pan to get to the filter, but it’d be much less messy to drain fluid first then drop the pan, rather than drop the pan with 12 quarts of fluid on top of it.

    And my experience, based on multiple Fords (and for Fords only), is that you either change it religiously at every 20K miles, or you don’t change it at all and rebuild at 100K.

    • 0 avatar

      If it has a pan, put a drain plug in it. Pan plugs are sold at parts stores, but avoid installing it on the bottom if possible, to avoid it getting sheered.

    • 0 avatar

      Some vehicles don’t even have a dipstick or a way to fill the transmission easily from topside. It wouldn’t be so bad if they simply had a drain plug and a fill plug like a manual, but they can’t even make it that easy.

    • 0 avatar
      Kevin Kluttz

      Or you could buy a Honda, which has a drain plug (3/8 drive ratchet fits) and a magnet on the plug itself in lieu of a filter. Seems to work, as I have a total of 333,000 miles on two Honda transmissions with no failures, and only a small glitch….
      About the transmission on my 2001 Accord (4-cylinder): I did the first fluid change on it at 145000, after it had already begun to slip on the 2-3 shift when cold, and only when cold-cold, like below 40 degrees and before warm-up. It shifted ok after reaching normal temperature. At 222000 I traded it with the original non-serviced transmission, slipping a little worse from age, but still shifting such that an average Joe would never have noticed. I had done two more fluid changes after the initial one.
      Don’t try to tell me that NOT changing my fluid is the way to go. I have proven to myself that changing the fluid is invaluable.

  • avatar

    GSlippy and Goldenhusky=100% correct.
    The 3 examples given in the 1st post were problem-child transmissions anyway. I could have retired rebuilding those old Subaru automatics back in the day.
    When the phrase “Dislodging the crud” is used, you have to ask yourself..”What is this crud and where did it come from?”
    It’s clutch pack material, metal from bushings, bearings etc. Which means this material is coming from parts that are on their way out anyway.
    Turn the statement around…if your transmission failed and your fluid was black as ink, you’d be kicking yourself for not having changed your fluid.
    Then too, if you had changed your fluid every 30K miles and your transmissions lasted 200K+ miles, you’d be posting that changing the fluid prolonged your transmissions life.
    Those trannies either died on their own or from neglect, not from changing the fluid.

  • avatar
    Gardiner Westbound

    The automatic transmissions in many newer vehicles are sealed, the fluid intended for lifetime use in normal operation. Unlike motor oil Automatic Transmission Fluid (ATF) does not have to contend with byproducts of combustion, condensation or nasty gases. It simply lubricates and cools. A filter traps and renders microscopic gear particles harmless. Change ATF only if specified by the carmaker, or if it has been overheated or contaminated.

    There is a real risk a well intentioned ATF change will be bungled. Transmission fluid is strictly car make and model specific. It must adhere precisely to the automaker’s formula. The manufacturer’s branded ATF is best. Never put multivehicle ATF into your car. Chain stores and franchised repair, tire and quick lube shops are notorious for it. Correct fill level is critical. Transmissions are unforgiving of fill errors.

    Drive gently for several kilometers after a cold start so the transmission fluid reaches optimum operating temperature before it is stressed. Use the brakes to slow the car on long downhill runs, not the transmission. Change gears only when fully stopped. Never “rock” a car out of snow, sand or mud. It will cook the ATF. A tow truck will be much less costly in the long run!

    Heat ruins ATF lubricity. If your car or truck is frequently heavily loaded, used as a tow vehicle or often driven in hilly country in hot weather install a good transmission cooler and change the ATF every 50,000 kilometers.

    • 0 avatar

      “The automatic transmissions in many newer vehicles are sealed, the fluid intended for lifetime use in normal operation.”

      Nothing to say to this and some of the other hogwash you wrote but B.S. Explain how the Esso synth blend AT fluid specified for my old “sealed for life” Passat transmission had an expiration date on the bottles but magically becomes “lifetime fluid” when poured into the transmission? Also, there are many excellent multi-vehicle ATFs that exceed the specs of the OEM fluids. The transmission in my Subaru has been working much better after switching from the old OEM syth blend fluid which was performing terribly since new to BG Full Synth universal ATF.

      There is no such thing as lifetime fluid….period.

    • 0 avatar

      I agree with everything you said, but what is “life” as in “Sealed For Life”? Most trannys will last 100K miles under normal use, on original fluid and that’s well out of warranty. A bonanza if they land back at the dealer for a new trans, especially German. Independent trans shops usually don’t rebuild German trannys and get them wholesale from the dealer. If they do rebuild, they still need various hard parts from the dealer at ridiculous prices.

    • 0 avatar
      Gardiner Westbound

      I have owned a couple of dozen cars, American, European and Japanese, typically keeping them about 200,000 kilometers. The long distance champ went 500,000 kilometers. Knock on wood, I have never needed a transmission repair.

      I changed ATF once, in a year old Acura RL I had to gently “rock” out of a snow bank, because Honda products are known for weak transmissions. I ponied up to have the dealer do it so Honda brand fluid was installed.

      Naysayers are free to service their cars as they see fit. This regimen has worked for me.

    • 0 avatar

      And an ideal wire has zero resistance.

      The D2 A8s came with a “lifetime transmission fluid”. The mean time to fialure on those un-fluid-changed 5-sp ZF units was around 120k miles. Hardly a “lifetime” for an all-aluminum $80,000 car. I sadly parted with mine when the second trans went out at 210k.

  • avatar

    I have had full service done on our 2002 CR-V and 2004 Impala every 30,000 miles. Our 2007 MX5 still has about 4K until its 30K service, but just got tires last Friday.

    Our mechanic warned me when he did a tranny fluid change at 60K on the Impala, I might experience some slipping.

    Does my tranny slip? Hmmm…some interesting things going on with my car, but I’ve experienced some slight slipping for years and it’s never gotten worse. When cold, when starting off from the first or second stop, I’ll give some gentle gas and sometimes experience a slip of sorts and when shifting into second, it kind of feels like a “rumbling” or hesitation, not quite finding the right term to use.

    No issues with the CR-V thus far – 97K.

    It’s never gotten worse, and at 100K miles, I’m tossing around how much longer to keep the Impala, as everything else is fine – and it looks gorgeous when clean – and really does run better, too – a “proven” fact!

    When mulling over this, wifey always says it’s cheaper to spend money on a tranny if everything else is OK than paying for a new car. BUT…most likely having to do my 100-mile-a-day commute for the next four years, would that justify another car or not?

    Sounds like a Piston Slap question in a comment, doesn’t it?

    Our 1990 Acclaim never had an issue with fluid changes and kept that car for 10.5 years, 138K miles. Same with our 1992 LeBaron convertible owned for 8.5 years, 1999-2007, 148K. The engine gave it up, though…

    So, should you change tranny fluid? My jury is still out – I think it’s kind of like the “luck of the draw”, that is, “[Condemned] if you do, [condemned] if you don’t”.

    • 0 avatar

      Did your Acclaim have the Ultradrive or the 3 speed? The 3 speed Chrysler units were indestructible…Mine never gave a hint of trouble for a 1/4 million miles. I’d swear there must have been some 727 DNA in there….

      • 0 avatar

        Both the Acclaim and LeBaron were 3 speeds. Yes, they were as indestructable as torqueflites of old.

        The 1993 Spirit did have the ultradrive with the 3.0L V6. That car was everything it turned out to be – junk! We bought that used and got rid of it a couple of years later before it cost us the farm, as the minute the tranny locked up in first, we got busy and found another car before it went belly-up. Dodged that big bullet.

  • avatar

    Definitely change the fluid if you’re not already having problems, however, it is true that if the clutches are already metal to metal, the dirty fluid will provide the needed friction to keep it going. Save the old fluid if it makes you feel better.

    I have been using the ‘special’ specific fluid when under warranty, but my trans guy says that’s BS to sell you expensive fluid.

    Depending on how hard it gets used or abused, change the fluid often and you will get close to a 100% exchange.

  • avatar

    No RFTOM recommendations?

    Rebuild kits are $400-500 plus labor. Cost to flush with new fluid is a little over $100. Your choice. Most have a banjo bolt to drain from, no need to drop pan unless your replacing filter.

  • avatar

    Either change it relatively frequently (every 30k or so) from new, or don’t change it at all.

    • 0 avatar

      Actually, a lot of modern transmissions do not even have a filter anymore as I found out when I had a transmission fluid change on my 07 Saturn Aura XR (6 Speed auto)at 100k.
      A Lot of shops advertise a trans flush, don’t know what the real difference is other than giving the impression that a ‘flush’ does more than a ‘change’

      • 0 avatar

        That is absolutely untrue. The 6T70 transmission in that car definitely has a filter. I know, I worked on that trans at GM and pulled apart a lot of them. The problem is, the trans has to come out of the car to change the filter.

      • 0 avatar

        “The problem is, the trans has to come out of the car to change the filter.”

        Wow… really GM?

        Can you just picture the design meeting conversation? “Oh we’ll just make the techs unbolt and drop the trans to change the filter, it would be too expensive now to go back and move it”

  • avatar

    I have a 2008 Pontiac g6 and a 2010 Dodge Grand
    Caravan, both do not recommend fluid changes unless you are under severe service like police or taxi cab use or towing. In fact, the Grand Caravan has a dipstick that says “Dealer Only” on it, so you can’t even check the level. Problem is, what does lifetime fluid mean, 100,000 miles, 150,000? 200,000? I think most manufacturers think 150,000 miles is a reasonable service life for a transmission.

    • 0 avatar

      …In my experience there no such thing as a lifetime fluid, that’s just Chrysler taking something out of your hands and putting it back into the dealers’. Change it often, minivans are just stretched cars using a car’s drivetrain, that transmission is already under a severe load towing the weight of itself and 4-8 passengers around.

  • avatar

    I remember when I bought my old Dodge Aries, the transmission fluid was that browny sh*tty colour, but it still shifted smoothly. I went and got a new batch of transmission fluid and the shifts became very harsh and lumpy both up and down. I didn’t get to see the transmission fail as other things failed first and I scrapped the thing. But I was still intrigued as to how and why that occurred. had various articles on the fluids you should use, but I also read various articles on not swapping transmission fluid once a car had got to the point where it had been neglected for quite some time, and various bits of testimony from various tinternet forums have backed that up.
    I’ll stick with manual transmission thank you. The only true way of messing them up is shifting like a complete tool.

  • avatar

    After reading all of this, I look back upon the cars my family has owned, and remember thinking that 211,000 miles was an awfully short time for a transmission to last before fifth gear got really loud, and 150,000 was a little early to be nursing synchros…

  • avatar

    I worked with a Chrysler “fluids and materials expert” and had this same conversation. She suggested the reason most cars suffer failure AFTER the fluid swap is because your local oil change places have a tendency to use any random trans oil they have on the shelf. The key to the argument was that a lot of engineering is spent on picking an oil to use in a modern transmission (this conversation happened about 5 years ago), and then after 100,000 miles of hard use, they’re replacing the stock oil with junk.


    Seems like a sound argument.

    • 0 avatar

      Frankly, that makes more sense than fresh factory-spec fluid killing a transmission. I can totally believe an unscrupulous oil change place pulling that, particularly if the consumer doesn’t pay attention.

  • avatar

    What about synthetic fluid?

    I have a 2002 Ford F250 Super Duty 7.3 with 205,000 miles on it. I purchased it at 191,000 and did a complete tranny service with Mobil 1 synthetic ATF. Haven’t had any problems and the tranny shifts smooth as silk.

    Two years ago I also purchased a 1995 Lexus LS400 that was apparently very well-maintained. Car had 80K when I bought it and is now up to 105,000. The tranny fluid is still fairly clean but its color has paled somewhat and it’s getting a bit of that “old” smell to it. Thinking of using synthetic in it also.

  • avatar

    Most automatic transmissions should have their fluid replaced every 30,000 miles and I mean ALL of it, not just whats in the pan.
    This is the correct way to do it per the Infiniti Factory Service Manual for the 2003 Q45:

    “To replace the A/T fluid, pour in new fluid at the charging pipe with the engine idling and at the same time drain the old fluid from the radiator cooler hose return side.

    When the color of the fluid coming out is about the same as the color of the new fluid, the replacement is complete. The amount of new transmission fluid to use should be 30 to 50% increase of the stipulated amount.”

    Nissan uses the exact same language is the FSM for the Nissan Titan.
    Fluid replacement is not very difficult to do, and anything less is a waste of time and money.

    • 0 avatar

      I’ve been changing all my tranny fluids every 30k miles. I usually drain and fill twice and call it good. No problems ever, and the shifts get better and feels more torque-y.

      But my new Infiniti has the new Nissan 7 speed AT. It’s basically a sealed unit from a consumer point of view. It has both a fill hole and a drain hole on the bottom of the transmission – yea, so not very useful. The FSM states there is a special tool that only dealers have access to (i.e. lots of $$$) which can do the fluid filling and level checking. You can MacGyver something to pump the fluid upwards, but it just sounds hacky. Also, the temperature of the fluid has to be correct as it goes in as it’s very difficult to check the levels given the 2-hole setup. I’ve heard of people actually begging the Infiniti dealer service dept to change their tranny fluid with $$$ in hand and they actually refuse to do it. They steadfastly claim that it’s a “lifetime” fluid (cough BMW claims the same thing cough)

  • avatar

    I bought my ’77 Chevelle from the 2nd owner a few years ago, and the trans wouldn’t go into reverse, nor would it go into 3rd. It was also very low on fluid. I did a fluid change just to see if I could save the trouble of doing a trans swap right away (already had one for it)

    What I drained out of it, I think didn’t see the light since Jimmy Carter was president. it was black and nasty. Put fresh fluid and a new filter, and drove it, it eventually gained 3rd gear and reverse, and then fried the forward clutch, so it lost all drive, but had reverse. It lasted about 5,000 miles, and no telling how far the previous owner drove it with it all screwed up since the speedo cable was broken, and the speedo gear was also broken.

    I don’t think changing the fluid hastened its demise. If anything it helped prolong its life a few more miles.

  • avatar

    Getting some new, proper fluid in there in place of the worn out, contaminated fluid isn’t going to hurt anything. I don’t think I’d ever pay to have ATF changed though. I don’t want any sort of flushing and I’d want to put the fluid in myself to know it’s getting the right stuff.

    Drain and replace. It doesn’t matter that you don’t get it all at once. Do it regularly and the fluid will always be in good condition: low on contaminants, at the proper viscosity, and with functional additives. I like the ones with a drain plug where I can just drain and replace a couple quarts every second oil change or so. $5 and 5 minutes a year to keep the fluid fresh.

  • avatar
    Kevin Kluttz

    Just change your fluid. Why else would they be selling it?

  • avatar

    My theory regarding the “fluid change causes problem soon afterwards” scenario:
    Many fluid changes are instigated by the owner noticing that the transmission doesn’t feel quite right. So they get a fluid change hoping this will magically fix the problem at minimum cost. When it craps out shortly afterwards the fluid change sometimes gets the blame. What really happened was the transmission was starting to fail and the fluid change made little or no difference.

  • avatar

    Original Poster Here! There are a few issues at play, and I think you’ve all mentioned them. 1) Bias to change the fluid only once a problem is detected. GUILTY on my 2003 TB….I did the change 2 months ago, slip got worse, cut my losses, driving a new 2012 Camry now. 2) The 89′ Sub, ’94 TB were used car lot cars – who the heck knows what was done to them before I owned them. I changed the fluid before detecting problems – most likely trans was at the end of the line anyway – coincidence?? 3) The 06 Odyssey – that darn torque converter seems to go bad for everyone – its worse every day, having trans fluid changed today with false hopes the problem lessens.

    I guess my personal dilemma is one of trust vs time. Its hard to find a mechanic you trust…..sometimes you may trust the head guy but he’s not the one working on the auto. Doing it myself….learning curve…Exxon Valdez in Driveway. Thus ignoring the issue until there is a problem, creating an even larger problem! The other factor is paying dealer vs doing it yourself. A rebuild may be less expensive than paying for 5 trans fluid changes (each 30k over 150k miles)unless you DIY – in this case – also Let ‘er ride!

    The ’12 Camry has no stated Trans fluid swap interval……let ‘er ride!

    • 0 avatar

      Let ‘er ride! Git er done! :)

      I’d rather pay for the regular fluid changes and risk wasting money than potentially being inconvenienced by a blown tranny and subsequent tow to the shop.

  • avatar

    Excellent topic for discussion since the automatic transmission is sometimes viewed a mysterious sealed unit which only the Hogwarts kids can conjour up spells to fix.

    The advice I was recently given from an Aamco owner who services all of my cars was “here [in Pittsburgh] you have extreme heat and extreme cold, the fluid in the pan [of a car] should be changed in no less than 25,000 miles”

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