Transmission fluid

[milarsky]

I have read basically every thread pertaining to this topic and am still confused. My M5 has 215,000 miles on her and I would like to change the transmission fluid. What are folks using for cars at this mileage?

best,
jeff

[Preyupy]

The same thing I put in them when they are new. I have had very good luck with Redline MTL on BMW/Getrag gearboxes, the cold shifting is good ( some of the thicker lubricants make it hard to shift cold) If you have oil leaks MTL will leak out just as fast as ATF but it’s no worse.

[milarsky]

Thanks so much. Folks have been recommending the MTL-LT-2-SAE 75W-80 for transmission and Fuchs Sintopoid Ls-SAE 75w-140 for the differential. No leaks in either.

[tn535i]

If you run mostly warm weather you might switch to MT90.
If you have more cold use maybe D4 ATF.
I would still recommend MTL as the all around-er and Redline as the go to.
Not many people seem to realize that at slightly different temperatures all three of these will have the same viscosity. And the viscosity change with temperature of any oil is quite large, so the trans will work with a broad spread of fluid properties.

For different behavior my son starting using Shock Proof in his Subaru (Subu folks seem to like it well) and he had good response. I am thinking about trying it in my M6 because it has a synchro that does not behave well and Shock Proof is supposed to have lower vis with higher film strength.

[Mike W.]

As tn535i suggested, there is no perfect answer. But I'll do the opposite on what not to use. Do not use a GL5 oil. That's fine for diffs, but not for Getrag trannys. The very properties that make it right for diffs make it wrong for trannys. MTL, MT90, ATF, Motor oil and more all are in the at least tolerable range, but not the thick, sticky GL5 meant for diffs.

What is the best for smooth shifting and bearing life? Easy, just like picking your favorite child.

[milarsky]

Thank you so much for the replies.

jeff

[EuroShark]

I've got Ravenol 75w80 GL-4 in mine and it's as smooth as can be. Amsoil MTG has also been very good in my 944 which requires GL-4. Shifting, especially when cold, is much smoother than with the Redline MTL I had in it before, for whatever that's worth.