8.75 rear oil for open diff

[chargd72]

Just picked up a 8.75 rear with 3.23 open gears.  Want to clean it up and swap out the 8.25 currently in.  What gear oil should I use?  Is friction modifier only for sure grip units?

Sure grip won't be added until more funds are available...

[randy73]

I just rebuilt my rearend and used 80-90 with friction modifier, but I went from open to SG, so you will not need the modifier.
My locker unit with everything to swap out was $425 from Cass, plus all new seals and crush leave.

[chargd72]

Thanks.  80w90 it is.