Here is what the Service Manual Reads on Diff Fluid Specs.
As taken from 2002 SERVICE MANUAL Jeep(R) GRAND CHEROKEE by DaimlerChrysler Corporation... Section LUBRICATION & MAINTENANCE
A multi-purpose, hypoid gear lubricant which conforms to MIL-L-2105C and API GL 5 quality specifications should be used. Mopar Hypoid Gear Lubricant conforms to these specifications.
- Lubricant is SAE 75W-140 SYNTHETIC
Note: Trak-lok(R) and Vari-lok(R) equipped axles require a friction modifier to be added to the lubricant
- Lubricant is a thermally stable SAE 80W-90 gear lubricant
- Lubricant for heavy-duty or trailer tow use is SAE 75W-140 SYNTHETIC.