Opie's reply,
"You need a 75w-90 GL5 for the diff.
The best ones are the Motul Gear 300, Red Line 75w-90 GL5, Fuchs Titan Race Syn 5, Millers CRX, Amsoil Severe Gear and Gulf Competition.
Castrol Transmax Universal LL/ Transmax Axle, Millers XF Premium MTF/ Nanodrive EE, Valvoline, Amsoil Severe Gear, Mobil SHC, Total Traxium Dual 9FE and Comma MV MTF Plus are also good options."