Is this a myth or fact. Read that flushing the trans fluid on a old car will make it worse.

 

myth..

 

Fact...
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Really depends on how it's done but it could be the straw that breaks the camels back. Search the word "flush" and read what other's have done. Most people drain and refill.

 

Personally I agree with a drain & refill. I'd avoid the vacuum flush method that many garages like to sell.

 

I'm a drain-and-fill guy, and I do my own work. Don't trust either the flush procedure or most of the shops who recommend it. No experience personally, but friends report hose jobs with disappointing frequency. I started doing my own work as a kid whose dad was willing to get me started and whose bank account wouldn't support others doing the work for me. Can now afford to farm it out, but have learned the hard way that I'm much better off doing it myself.

Lynn B.

 

Not in my world. I worked for a fleet service company with over 1 million vehicles. Those varied from little econo 4 cyl two doors to class 7 tractor trailers.
I'm ASE certified in cars and trucks and my job was to determine if the repair or maintenance request from the shop made sense and was within each fleets parameters. A lot of the fleets let the vehicles go before 70 or 80 K so they didn't want to spend the money on transmission services.
On vehicles with over 100K and no transmission service history we would routinely deny any attempt to power flush a transmission due to the recorded and documented failure rate of the vehicles that did receive this service.

Now having said that I self flushed my transmission when I first bought my 850 because it was black and I couldn't stand it. I had no history but from the looks of the $350 dollar beater I'm sure nothing was serviced unless broken so at 260K it was a gamble. I did pretty much expect it to start slipping but 30K and two years later and I'm getting ready to do it again.

 

I've read tons of info on this as I 'm sure many of you have. And this discussion could go on forever. To me it looks like a crap shoot depending on a list of facts behind the history of the vehicle. To be absolutely safe, if you know nothing about the history, do a drain and fill if you feel you MUST get some fresh fluid in the trans. If all goes well do it a couple more times! Anybody disagree with that approach? I did this on my 180k miles 850NA and it's perfect.

 

A friend who has sold auto service tools and equipment to dealers, garages, and parts houses most of his adult life says that the reasoning behind flushing is that it's "non-invasive" to the trans. If, during servicing, the pan is not removed and no parts are exchanged, then any trouble that crops up for the customer afterward is plausibly deniable by the servicing agent. "Hey, all we did was replace that scorched molasses you had in your transmission with the best trans fluid on the planet! And if you'd have let us service your trans from the time it was new, it'd still be in great shape! We didn't TOUCH anything inside your trans, so it ain't our fault!"

Such is the stance with most of the shops I know. Those that I avoid, anyway.

Lynn B.

 

I'm with you. A drain and fill is the safest way to introduce fresh fluid and I do feel it's a good thing to do. It's the same as changing engine oil or any other fluid. The stuff does break down over time and it picks up debris from the components wearing out and can then accelerate that wear.

For me I'd just more comfortable taking off the cooling hose to the radiator and letting the transmission front pump do the work. Half an hour of my time, nine or ten quarts of fluid and the stuff is near new pink !!

 

Dear Lynn, that "non-invasive" power flush that all the quick lubes try to push you into is better than nothing but on my other cars I can't understand the value of flushing the fluid and leaving the filter in there anymore than doing an oil change for the engine without changing the filter. Sooner or later it's going to cause a problem.

 

is IPDS way of changing the fluid the best way? with the provided transparent hose?

 

I like that way best but the drain and fill is Rspi's preferred way and he has almost 10X the posts I have.

I just used a piece of water softener green transparent drain hose I had laying around. That and a 5+ quart oil jug that has a clear strip that's graduated. You measure what comes out and add the same. That way you're closer to where you need to be when you get done. I still checked mine for the next couple days in case it "burped" some air out of someplace. The hose was the perfect size to fit tightly onto the end of the metal line. You don't want that sucker coming off I reused the seals and clips but I have bought new seals and when I do the next one this fall I'll make sure to get the new seals in there. The other trick is to make sure you have the output hose and not the inlet. On my 95 850 it was the upper hose that had pressure and I left the cooler fitting on the radiator open as it's a return to the transmissions sump and doesn't have any pressure. I did hear a horror story of someone who pulled the wrong hose and you can imagine the mess it could make spewing trans fluid out the opening of the radiator all over your engine, you and the floor I think it's the 70 series that is backward and it's the lower hose you pull but MAKE SURE.

 

I have read several people that wrote that they did the line method where they got all or close to all of the fluid changed at one time. If you are not having any issues, I think that would be great. Also, if you can add fluid while you're draining fluid, I think that would be awesome. I just don't like the flush, where some external source is applying pressure to the system.

 

The one thing I forgot was as it's sitting there idling pumping fluid slowly row it through the gears. That way you are sending fresh fluid through all the passages in the valve body too