M5R1 Trans Reassembly and Lube

[Shran]

I've used sythetic 5w-30 in them, it cured a lot of shifting issues in one trans but made no difference in the rest. Let us know your results.

 

[PetroleumJunkie412]

Interested as well. 1990 M5 only likes Mobil synthetic atf, and 2011 m5 seems to hate everything. Curious to results.

 

[DPDISXR4Ti]

2.75 quarts of Synthetic 5W-20 went into the M5 yesterday. Shifts great, but I wasn't surprised by that. I'll try to remember to come back here X years from now with an update. The likely reality is that this will be the fluid this truck goes to the grave with one day. Hopefully it won't be the reason! Doubtful that would be the case.

 

[Country boy 1975]

i just swapped a m5r1 from a 92 2.9 into my 91 4.0 and filled with 3 qts of royal purple synchromesh. My god the price for that stuff! I'm not sure if i'll buy again, no problems running it yet, but I'm wondering how much of that price is for using the name.

 

[4x4junkie]

I have Royal Purple fluid in my BII's M5OD ( "Synchromax" fluid).
I think it was ~$16 each for three quarts I paid a few years back... That doesn't really seem like much of a burden to me, especially when you compare it to the more than $8300 you'll put into your truck's fuel tank during the 60K or so miles you'd typically leave it in there before changing it out again (assuming $2.50/gallon and 18 MPG).

It seems I did notice a very subtle uptick in power delivery in 5th gear after putting it in (and also what seemed like maybe slightly lower temps), which would make sense since it is touted to reduce internal friction somewhat (and therefore wear) vs with conventional Mercon fluid.