CSCHWER,
There are two different 75W90's
1. 75W90
2. 75W90NS (no slip)
I was told that if I used the 75W90NS that I would need to add a friction modifier, which is needed for limited slip differentials.
The straight 75W90
has friction modifiers in it already, so I am waiting for this type to come in.
Are you using the "NS" type
oil and if so how is it working and did you add any friction modifier??
Thanks,
Jack