[Blk5er33]

I have a 6MT '21 M4 with ~15K miles. It has been to 4 track days last year and plan to do 8-10 days this year. Is it worthwhile to change diff and manual trans fluid once per year n a car that is both a daily driver and weekend track car? And if so, which specific fluid is needed?

A search on Turner motorsports yields this: https://www.turnermotorsport.com/BMW...erential-fluid

And bimmerworld recommended this for trans fluid:
https://www.bimmerworld.com/Red-Line...uid-Quart.html

And this for diff:
https://www.bimmerworld.com/Red-Line...Oil-Quart.html

Not sure if this is correct though.

[doctor_tran]

Also looking for this information.

[doctor_tran]

I believe the part numbers are as follows:

BMW MTF-LT-5: 83222239654 (1.6L needed so x2 bottles)
BMW Hypoid Axle Oil G4: 83222447362 (1.5L needed so x3 bottles)

[Blk5er33]

Originally Posted by doctor_tran

I believe the part numbers are as follows:

BMW MTF-LT-5: 83222239654 (1.6L needed so x2 bottles)
BMW Hypoid Axle Oil G4: 83222447362 (1.5L needed so x3 bottles)

Thank you! I have been unsuccessfull in finding it so far.

[doctor_tran]

Seems like an alternative part number for the MT fluid is 83222156969

[doctor_tran]

Just did the diff and transmission fluid along with an extra oil change at 5k miles.

Definitely some metal in the diff so worth doing the fluids despite having the diff fluid changed at break in.

It was super easy for both with plenty of room so you don't need any special low profile hex sockets.

[somer]

Originally Posted by doctor_tran

Just did the diff and transmission fluid along with an extra oil change at 5k miles.

Definitely some metal in the diff so worth doing the fluids despite having the diff fluid changed at break in.

It was super easy for both with plenty of room so you don't need any special low profile hex sockets.

You think about getting one of those magnetic diff oil drain plugs?

[dimab0]

Originally Posted by doctor_tran

Just did the diff and transmission fluid along with an extra oil change at 5k miles.

Definitely some metal in the diff so worth doing the fluids despite having the diff fluid changed at break in.

It was super easy for both with plenty of room so you don't need any special low profile hex sockets.

I'm still unclear about how often it is recommended to change the rear diff fluid. I don't see it mentioned in the service manual. My car does have some track days to it and when cold I now hear a clunking noise from rear when turning, until I suspect the fluid warms up. The dealer, of course, thinks it's unrelated to rear diff fluid....

[dimab0]

Originally Posted by dimab0

I'm still unclear about how often it is recommended to change the rear diff fluid. I don't see it mentioned in the service manual. My car does have some track days to it and when cold I now hear a clunking noise from rear when turning, until I suspect the fluid warms up. The dealer, of course, thinks it's unrelated to rear diff fluid....

I convinced the dealer to change the rear differential fluid. So far I think that has resolved all of my clunking noises. The car has about 30k miles on it.

[geko29]

Originally Posted by dimab0

I'm still unclear about how often it is recommended to change the rear diff fluid. I don't see it mentioned in the service manual.

Diff fluid and Transfer case fluid for xDrive models is indicated at the 5th oil change or 50k miles. Maintenance schedule does not list trans fluid at all.