Hi, I bought some Auto-RX for my Caddy Northstar, but i am afraid to do the transmission treatment when the trans is shifting perfectly fine. Is there ANY chance auto-rx could shake something loose? I heard that if some gunk in the trans is holding clutch packs together, flushing them loose would mess up all the shift circuits and everything would slip?
If it really will not hurt anything i would love to do a treatment if it means some extra miles out of the trans.. Thanks
Unlike engine oil, transmissions are not in the presence of any hydrocarbons and whatnot from the combustion process. The only "gunk" in a transmission will be clutch material. Most of it will be picked up by the magnet at the bottom of the pan. I've never heard of it holding clutch packs together and if it breaks loose the transmission slips - it's hogwash.
I am confident it will not hurt anything. Just follow the application instructions.
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Bought a 145,000 mile 1993 Buick Century with no knowledge of previous maintenance, but the trans fluid was very dark. The transmission functioned fine. I replaced all the fluid, and the next day the car would fall into a false neutral at every stop. I would have to shift to park, then back into drive in order to get it to move. Took it to several transmission shops, and every one of them said I should not have changed the fluid at all, similar to what you have heard. They all said I needed a new transmission. After a month of this, I added 4oz of autorx. The next day the car started shifting normally again. That was 20,000 miles ago and it has been perfect ever since.
So I would say yes, there is a chance that making any change to your fluid might cause problems, if the fluid is old enough. However, if you don't change it at all, you are also likely to develop problems since cars need good fluid. So its a catch 22.
Some manufacturers say that the fluid never needs servicing. I don't buy that. I see many lexus rx300's over 100k with transmission problems where the fluid is original. Lexus says never change the fluid. We change ours (drain and fill) every 30k.
Given the above, what I do now with a car with very old fluid is to do a drain and fill (as opposed to a flush) which only replaces a fraction of the fluid, run it like that for 1000 miles, then add autorx as per instructions, then do a full flush after 3000 miles. This is a gradual method, and seems safer.
Do an internet search and you will find many instances of people having problems when changing their transmission fluid for the first time when over 100k miles. If you have been servicing the transmission regularly, I see no risk at all
