Fluid help

[Carves]

Based on your intended vehicle use ...

an 80/90 diff oil should be adequate.
If you have a LSD rear ... you need to use an additive ... or buy a diff oil with it already mixed in it.


Some factory info as a guide ...

LUBRICANT SPECIFICATIONS

A multi–purpose, hypoid gear lubricant which conforms to the following specifications should be used.

Mopart Hypoid Gear Lubricant conforms to all of these specifications.

The lubricant should have MIL–L–2105C and API GL 5 quality specifications.
Lubricant is a thermally stable SAE 80W–90 gear lubricant.

Lubricant for axles intended for heavy-duty or trailer tow use is SAE 75W–140SYNTHETIC gear lubricant.

CAUTION:

If axle is submerged in water, lubricant must be replaced immediately to avoid possible premature axle failure.


Probably be worthwhile considering 4x4 as "heavy-duty" ..

Tranny oil is an ongoing debate .... DexMerc was the original spec ... and for better or worse ... I just run Valvoline DX3.

.