On to my next project. Car has 55k miles. Was thinking of using Redline for both. Wanted to use 75w90 on the diff. Is that OK? What about trans fluid? Also, is there a DIY for trans? Is there just a drain plug, then fill till fluid comes out plug? Advice? Thanks guys.

 

https://5series.net/forums/topic/881...3#entry1281673

No need to do differential fluid you'll waste your money....Now that fluid I do agree is lifetime. I changed my differential on my E46 with like 120K+ miles and it could have been re-used. Seriously...read bout it first because you'll see majority agrees.

 

No Fluid is lifetime. Change you transmission and diff at 50k. Redline 75w90 is good. I'm going to use the same fluid in mine. The tranmission oil is tricky. Buy the oil from the Dealer or RM European. Good Luck

 

I used RedLine in my differential.

The tranny fluid gets tricky as you'll see if you read the transmission fluid change link as posted above.