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So I've heard its unwise to change the trans fluid in an auto if the same fliud has gone well past the change interval as the tans might wear faster with new fluid.
My AW70 shifts fine but I want to flush the fluid but not with consequence. So is this fact or myth?
Also what fluid do you guys use?
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I always take the chance and change out my auto tranny fluid on a new to me vehicle. The inlet filter on all the AW70 and 71 trannies is good for keeping boulders from circulating around, not much else. That being said, I'll usually drop the pan, clean it out, change or clean the filter, and reinstall a new gasket. I then do as one of the other respondents here (Ken C) does, which is to add Amsoil and flush all the old fluid in it out that way. Sometimes I'll get really fancy and attach a magnet onto the pan on the outside, awaiting the next fluid change. Heat probably is the number 1 killer of automatic transmissions, followed by old, worn out fluid.
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I agree that it is better to change out old fluid, rather than leaving the old stuff in.
I drop my transmission pan every 20,000 to 25,000 miles and clean the filter. Just a little black film in the bottom of the pan. This method drains about 4 quarts of ATF fluid.
Luckily, I added a genuine Volvo automatic transmission cooler back in 1993, when the car had 60,000 miles. The unit drops the temperature 28 degrees, in the summer time.
Heat is one of the main factors that kills automatic transmissions, and I am at 352,808 miles, on the original transmission. I'm sure my fluid change intervals are pretty conservative, but I'm all for cheap, preventive maintenance.
--
If it needs to be maintained, repaired or replaced on a 1990 240, I've probably done it. '90 240DL, 352,808 miles, will she make it to 400K ?? >>You haven't really worked on a car until you draw blood<< :-}
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Agreed. I've been installing them in all my cars since I owned an '84 (which I used for towing one of my small boats); they're also on my two '93s, even though I don't use these for towing, but, along with using AmsOil synthetic ATF, just to keep the transmission lasting forever:
It can be seen here incidentally, just to the driver's side of the four horns (and in front of the auxiliary fan) that I installed which was the original focus of the picture:
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It's total myth.
I change my fluid as soon as I buy a used car. And my personal preference is AmsOil synthetic ATF but it's very expensive, and you can use anything that you can afford. Whatever you use, it's better than the old fluid in there.
But also know that it takes a lot of quarts to run through if you use the "flush" technique (2 qts added at a time,draining at the radiator connection) -- because every addition is mixed and diluted with the old fluid, so for example to actually change the total of 7.4 qts in the transmission and torque converter, you actually have to run through two cases (24 qts) to get 95% of the old fluid exchanged. To reach 99% changed, you have to run through 32 quarts.
You didn't say what model year, but remember that up to and including '83, you want to use Type F fluid. From 1984-on, you want to use Dexron.
Good luck with your new car.
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KenC, you are "mathematically correct" about the volume required if you assume that complete, homogeneous mixing occurs between new and old fluids as soon as an amount of new fluid is added. This would happen if you drained and replaced 1 litre, ran the engine for a bit, repeated, etc. But of course that's not how we do it, when following the recommended method.
In fluid flushes I have done on the AW trans's I have observed a rather sharp transition from the old fluid to clear, red fluid at about the 10-12 litres/qts point. It is not a piston-like displacement, but it's closer to it than a homogeneous mixing model. So I stop there, as it sure looks like fresh ATF is being pumped out and into my waste container.
And just for info to the BB in general, the specs of the latest Dexron (VI) are pretty close to those of the synthetics and the price around here is less than half. Hence, my choice.
--
Bob: Son's XC70, my 83 240, 89 745 (V8) and S90. Also '77 MGB and some old motorcycles
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Myth, with a caveat: fresh fluid can conceivably knock loose crud, which will accumulate in the pan, and possibly clog up the filter. If you flush an old tranny for the first time, drop the pan and change the filter too.
By the time most people try flushing their tranny, it is already showing signs of failure, and usually fails soon after.
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I agree, urban legend, unless your tranny is already half past dead. I've recently flushed my 850 that had been last serviced who knows when. Shifts great, fluid is nice and red. I'd flush it if it's due. Good luck.
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Urban legend, I would say. There will always be a story or two of a part that failed after some perfectly reasonable maintenance item was performed. You have to believe the part was about to fail anyhow. Check the appearance of your fluid. If it's red and reasonably clear, leave it be. If it's brownish, muddy, or smells burnt, change.
I have done numerous flushes and refills with fresh ATF on high-mileage cars with no problems.
The procedure to flush the old fluid and do a complete change is in the 700/900 FAQ's accessed from the drop down list at the top of this page (see: "more"). If your car is 1984 or later, the recommended fluid was Dexron-II or III. This may be getting hard to find since GM (holder of the Dexron rights) no longer support or monitor the spec. Dexron VI is the new version, is compatible with Dex-II/III/IV etc. and has superior properties in a number of departments.
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Bob: Son's XC70, my 83 240, 89 745 (V8) and S90. Also '77 MGB and some old motorcycles
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