Diff lubricants recommended when ARB lockers installed:

Normal/Typical
Shell: Diff Oil (SAE 90)
Mobile: Mobilube GX90

Heavy Off Road Use
Shell: Spirax HD 85W-140
Mobile: Mobilube GX140

High Temp/Desert Use
Shell: Spirax S 80W-140
Mobil: Mobilube SHC 80W-140

Low Temp/Winter Use
Shell: Spirax S 75W-90
Mobil: Mobilube SHC 75W-90

Courtesy of ARB Locker Operating & Service Manual

Notice no friction modifiers in the rear when an LSD is upgraded to a locker.

1990 Monty LS 3.0 A/T LWB. KYB front shocks, OME rears and coils. 33x10.5 BFG Muds. 5.29, 2.85, RD110, RD46. 2 bouncys. Aisins. Monte Disco swaybar disconnects. GenII t-arms, idler arm, UCA's, V45W front brakes. 2in BL.