By on August 3, 2011

Jackson writes:

I own a 2001 Nissan Maxima and a 2006 Corvette, both purchased new w/cash. I know the Maxima with 105,000+ miles has had two ATF services, which included the “dreaded ATF Flush”. So far the thing keeps running, only issue (unrelated) was a Cat replacement (99,000) and 3 O2 sensors around the same time.

The 2006 Corvette at 5 years and 42,600 miles is due for a coolant service and I see that the ATF service is 50,000 (harsh) or 100,000 (normal). So far expenses have been limited to gas, once a year oil changes and a set of tires at 26,000 due to some aggressive driving, aggressive factory camber settings and a shard of metal. It’s been spotless so far besides a squeaky roof panel which has been solved by periodic application of Super Lube to some contact points. Should I do an ATF flush for the vette? It would be a BG machine. It’s a warm weather commuter for me (42 miles round trip per day of which 26 is highway miles on which avg. speed 75 mph which is just 3 days a week).

I have taken it on 6 long trips over the years as well as weekend cruises. I do use the paddles about 30% of the time, but do not really hoon it so much the past 2 years after getting 3 speeding tickets in 6 month period…which I fought and is another subject. So please advise.

Sajeev answers:

The easier of the two to E-diagnose is the ‘vette. First, I really hope you ditch(ed) those run flat tires for some donuts befitting a Porsche 911, as that is what the Corvette deserved from the factory. And like much like Motor Trend’s game changing car of the year, the 1997 Chevy Malibu, the C6 Corvette comes with a sealed-for-life transmission. Which begs the question, where did you hear about a 50,000 mile service interval under any condition? Not that owner’s manuals are always right, but I seriously doubt you read that from your glovebox.

These gearboxes normally go 100,000-ish miles before servicing, and your driving habits are definitely within that realm. If you have the motivation, check the fluid’s condition using the link’s info. Odds are the ATF is fine, it should have a pink color with a slightly sweet smell. If it has black-ish bits and smells like a BBQ pit, change it according to factory procedures…and good luck with that!

Now about the Maxima: I question if an “ATF flush” is really something to dread. I’d be quite thrilled with your vehicle, if I were to buy it from you. The biggest plus in the flush’s favor is how it blows out all the old fluid from the torque convertor, which is essentially impossible in vehicles without a drain plug on said convertor’s case. While it doesn’t change the transmission filter, I’ve been told by several techs that this filter isn’t exactly that high tolerance in its filtering capability. Which implies…

…that doing the “dreaded ATF flush” when your fluid degrades essentially makes the transmission filter a lifetime service part. My thoughts are completely debunked over here, but I see their opinion as more applicable to car with more advanced transmission failures.

What say you, Best and Brightest?

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry.

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17 Comments on “Piston Slap: Dreading “The Dreaded” ATF Flush?...”


  • avatar
    zerofoo

    One of my buddies is a mechanic. On his personal vehicle he runs the T-Tech machine, pulls the pan down, replaces the filter, puts in a new pan gasket then fills the transmission with fresh fluid.

    Overkill? Maybe, but transmissions are expensive.

    -ted

  • avatar
    vbofw

    My ATF fluid is purported to be “lifetime” per the manual. My techs including one at the dealer stick by this even with my car at 170,000. They say it’s not worth the risk to touch it.

    Same with the fuel filter, funny enough. Lifetime. I’m continually surprised by this.

  • avatar
    GeeDashOff

    If its available check the service manual and maintenance schedule for the cars. The maintenance schedule for my car lists ATF service every 30k miles (for harsh driving), but the service manual says to only do a drain and fill, no flush needed, especially no dropping of the pan needed, and the filter is a no-service part unless it gets physically damaged somehow. YMMV

  • avatar
    Zackman

    I’ve had the fluid changed in my Impala and I was warned by my mechanic that it might slip a bit. It doesn’t act any different than it always has, so I suppose it is O.K.

    I’ve also had coolant changes/flushes as well. No issues on any car I have owned.

    Sealed for life? Who’s? I’d be concerned by that, but I’m not familiar with such a thing, either. Like ball joints and other parts that no longer have grease fittings on them.

  • avatar
    SP

    If the Vette manual says to replace the filter … then do it.

    I don’t care for flush machines. In my opinion, if you want to eke the maximum lifespan out of the car, then do fluid & filter changes on some regular interval, like 30-45k miles. If you are generally neglectful, then don’t change the fluid, ever. Just leave it alone.

    The only thing that I will say you must do either way is keep the fluid level correct. If you have a leak, fix it ASAP.

  • avatar
    tresmonos

    Cavalier with the GM 4T40. 165K without flusing the ‘life time fluid’ form it. The trans is the least bit of my worries; still shifts like it always has.

    The car leaks no fluids (except oil seepage around the head), so SP’s advice is spot on, IMHO.

  • avatar
    Scoutdude

    If you want to do it do it right, drop the pan and change the filter(if that Vette has a filter than can be changed w/o tear down). Transmission flush machines do not change all of the fluid and leave a ton of dirty fluid in the converter. You end up with about the same 50% of the old fluid in the trans. The difference is that you don’t have a clean filter, the debris was not cleaned from the pan or magnet, and you paid for a bunch of new fluid that ended up in the waste tank of the machine. Oh and your wallet is usually thinner than doing it the right way.

    • 0 avatar
      Exfordtech

      Umm no, a flush machine that relies on only the pressure generated by the transmission’s own pump will purge virtually all of the fluid when connected in line with the trans oil cooler provided tthe service is done correctly. The vehicle needs to have the drive wheels off of the ground, the transmission must be brought to proper operating temperature (light brake torquing at about 1000 to 1500 rpms will accomplish this quickly) to ensure any thermostatic bypass valve is opened, and then the vehicle is run through all it’s gears repeatedly until the transfusion is complete. Also use NOTHING in the machine except the factory fluid. The chemistry of transmission fluid (and engine oil as well but that’s another topic) is way too complicated to risk the purported benefits of the snake oil salesmen (BG’s, Wynn’s etc.) against what likely millions of dollars the manufacturer spent in the design of the transmission components and their relationship with the specified fluid.

    • 0 avatar
      Exfordtech

      Umm no, a flush machine that relies on only the pressure generated by the transmission’s own pump will purge virtually all of the fluid when connected in line with the trans oil cooler provided the service is done correctly. The vehicle needs to have the drive wheels off of the ground, the transmission must be brought to proper operating temperature (light brake torquing at about 1000 to 1500 rpms will accomplish this quickly) to ensure any thermostatic bypass valve is opened, and then the vehicle is run through all it’s gears repeatedly until the transfusion is complete. Also use NOTHING in the machine except the factory fluid. The chemistry of transmission fluid (and engine oil as well but that’s another topic) is way too complicated to risk the purported benefits of the snake oil salesmen (BG’s, Wynn’s etc.) against what likely millions of dollars the manufacturer spent in the design of the transmission components and their relationship with the specified fluid.

  • avatar
    anonymic

    There are simple rules to trans flushes and pan drops, and caveats as well.

    If the fluid smells burnt or resembles used oil, it’s done.

    If it has any kind of black or brown flecks in it, your filter is likely clogged, and the fluid is done.

    If it smells sweet and has a red or orange-ish hue to it, all is good.

    In the first case you can do a pan gasket & filter or a flush, or both, but do the flush first otherwise your new filter will load up with whatever junk is in the fluid during the flush.

    In the third case, you’re golden. Keep it full and check the quality of the oil occasionally.

    In the case of any clutch media in the fluid as in the second case, or metallic bits in the fluid, take it to a proper transmission shop to have it diagnosed. Sometimes (though seriously not often) a transmission needs that crap in the fluid to keep functioning properly. This is a case of the car that’s held together by the dirt.

    Pay the transmission guy to look it over, it’s cheaper in the long run, if you have a transmission held together by the dirt, you don’t want to pay for a new autobox that failed on the way home after a flush. If he recommends a flush, ask if he’ll give you a guarantee. If the recommendation is to forgo the flush, it might be a good time to trade the car in.

  • avatar
    Kabayo

    I drain the 2.5 quarts of ATF which will come out (half its capacity) with each oil change, and I refill it with Mobil 1 ATF. It has taken me four changes to get over 90% new ATF in there, lol.

    My car is a 1991 Mazda MX-6 GT. The tranny is a different unit than in the non-turbo cars, and hard to find in junkyards. I don’t want it to fail – ever. There was nothing at all on the magnetic drain plug at the last change (about 6000 miles), so – so far, so good.

    I have 90,000+ miles at the moment. Bought the car for $1,400 with 74,000 miles four years ago. Such a deal. I consider the 88-92 626/MX-6 to be overbuilt cars, and good for at least 200,000 miles with no major repairs. The turbos were little known sleepers in their day, especially the 626s. I have had several of them.

  • avatar
    DIYer

    I like the old school way of dropping the pan, wiping out the sediment, and putting a new filter in. I do this every 75,000 miles (halfway between harsh and normal). It’s not difficult to do yourself, and I’ve never had any problems, costs around $50. An independent mechanic will charge $175 for this. I’ve never take any vehicle in for a flush, but it is a cheaper way to go, around $120. A dealer garage will charge you more for each, of course – (and probably recommend new brakes and struts while they have it up on the rack).

  • avatar
    tiredoldmechanic

    In my experience, trans flushes are nothing to be afraid of if you have maintained the trans properly (eg. filter change and fluid replacement). It sounds like you have done so to the extent possible with your cars.
    The problems start with units that have 200,000 km on the original fluid and filter and then the owner gets talked into a flush at the shop, or else the flush is a “hail Mary” play to try and remedy a slipping or run hot problem. In those case a flush can accelerate problems that may have gone awhile longer otherwise. That old Fram filter ad had it right, you can pay a little now or a lot later.

    • 0 avatar
      MBella

      Yeah, what he said. It’s good to do regularly. The brown burnt fluid that Sajeev was taking about is when you should have second thoughts about the flush.

  • avatar
    cardeveloper

    Trans flushes can dislodge material that can cause other issues. Just drop the pan and change the oil. If it’s really bad, do it again in 1-2k miles.

  • avatar
    CougarXR7

    I’ve never liked machine flushes due to the fact that they completely ignore the gunk trapped in the filter and the bottom of the pan.

    I plan on flushing and filling my 101,000 mile ’95 Lexus LS400′s tranny 3 or 4 consecutive times with Mobil 1 ATF.


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