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Discussion Starter · #1 ·
How often should the automatic tranny fluid be changed in a 900 t? Some transmission shops power flush the tranny so you get all new fluid vs a normal drain which only changes a small percentage of the old fluid. I am a bit leary of the power wash on a high milage tranny. Thoughts?
 

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How does the power flush work? The method I've used is to change the fluid, drive for 30 minutes / miles and drain again. Properly speaking a third drain at a thousand miles or so later should happen but that seems like it wouldn't help that much.
 

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Discussion Starter · #3 ·
The shop hooks up both an inlet and and an outlet hose (drain) and then pumps new fluid into the tranny forcing the old fluid out. Basically you aren't replacing just 4 qts or so but all of it, as 3/4 of the old fluid stays in the tranny with a normal drain/flush.
 

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I'd change the fluid, and filter, every 100k miles. You don't need to do it any more often than that, but check fluid level evrry time you do an engine oil change to make sure you don't run low.

Unlike what some say about a manual trans, changing the fluid in an automatic will not cause problems regardless of its age.
 

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Discussion Starter · #5 ·
ProfZ said:
I'd change the fluid, and filter, every 100k miles. You don't need to do it any more often than that, but check fluid level evrry time you do an engine oil change to make sure you don't run low.

Unlike what some say about a manual trans, changing the fluid in an automatic will not cause problems regardless of its age.
The local Saab shop says every 50,000 miles or so?
 

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I've had automatic Saabs since about 1979. When I first get one, I drain the fluid (what I can) and replace. Then drive around for a few miles, and repeat the operation. Then do it again. By that time, most of the fluid has been replaced and the fluid looks good.

Rule of thumb for transmission using non-sythetic ATF--
rear-wheel drive, drain the pan at least every 25,000 miles or 2 years
front-wheel drive, drain the pan at least every 15,000 miles or 2 years.

As soon as synthetic ATF becam available from AMSOIL, I changed all the fluid (three pan drains), and then ran for as long as I owned the car with only some minor fluid replacements from leakage or seepage. In theory should probably drain the pan and replace fluid every 45,000 miles or 6 years.
 
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