You can run Mobil1 75w90 LS Synthetic in yr diff!
You can just run Mobil1 Synthetic LS 75w90 in the diff. Synthetic oil additive packages work just fine with LSD's.

Originally Posted by
Ross
Denny,
If you have an LSD the only noise it will make specific to the LSD is clutch chatter. This is what the additive is for. Usually it will chatter during the first turn after driving straight for a while. The additive AND fresh fluid should improve that.
If it grumbles all the time while accelerating you may have a pinion bearing failing. A failed bearing will leave metal in the gear oil as evidence.
"Uncle" Phil C
2011 Kia Optima EX-P.
Former owner of a 95 525i 5spd. "The GQ" aka A Shark in sheeps clothing
03 R1150RT 6spd. "DaRTth"
00 R1100R 5spd. "LeRoy"