Tranny fluid question for the experts

[Cookie]

Late model BMWs with the high performance ZF five
speed have an interesting problem. A spring that centers the linkage is a bit weaker than it should be. In cold weather the cars sometimes will not center properly, and if the fluid has not been serviced on a regular basis they can stick in warm weather. BMW's cure is to pull the transmission and replace the spring. Since I have seen a couple cured by new oil,I wonder if the cold weather sticking could not be helped by lighter oil.
In the past this was no problem when you ran 80 or 90 but these transmissions run ATF. Question, what is the lightest ATF?

 

[HardbodyLoyalist]

What type of ATF do the specs call for?

ATF+3/+4? Dexron III? Type F?

As a side note, most ATFs have a viscosity of around 7 at 100C, which is solidly in the SAE 20 range. I'm not sure that going thinner is the best solution to your problem. You'd probably be better served by just using a full synthetic (group IV/V) ATF.

 

[porcupine73]

Sounds like potentially a good application for Specialty Formulations MTFGlide ?

 

[Cookie]

Most of the folks I know use Redline D4ATF so I imagine that meets the BMW spec. BMW just calls thier fluid lifetime fill I think. I agree that the MTFGlide looks very interesting. Do you know anyone who has used it?

 

[porcupine73]

If you search for MTFGlide it will bring up various posts such as this and that.

I'm sure MolaKule could tell you if it would be good for your application.

"MTFGlide has the same viscosity as ATF fluid but five times the anti-wear additives and a GL4 EP additive package." mmmmm...makes my mouth water.

 

[Cookie]

Thanks guys.