...but it came with a manual, just like any one of my jeeps did. Figure out what you have,what it does and how to maintain it...
Okay, while my Jeep is a 2003, the manual that came with it is for a 2004, which really should be the same (no major differences between the years). They refer to the Locking Axles in the Rubicon as Tru-Lok. They refer to the limited slip differential as Trac-Lok. The manual isn't specifically for the Rubicon, but since they reference the lockers, I'm hoping it applies.
Under
Recommended Fluids - Axle Differential (front-rear) it says:
Mopar Hypoid Gear Lubricant (SAE 80W-90) (API GL5) or equivalent. For trailer towing, use a SAE 75W-140 Synthetic Gear Lubricant. Models equipped with Trac-Lok require an additive.
So that's fine and dandy, I can go out and buy any API GL5 certified 80W-90 gear oil, but then I was reading that:
- the limited slip additive for Trak-Lok can actually damage the lockers (Tru-Lok) in a Rubicon (no citation, can't find the link), and I know some gear oils come with it pre-mixed (my car has front and rear limited slip differentials and the gear oil I'm using in it comes with the additives premixed)
- some people say the additive won't hurt anything, but don't specifically say this for Rubicons, so they could be talking about open D35s or the optional open D44s on some TJs.
- as well as towing, other "heavy use" situations should use the 75W-140 synthetic oil, i.e. offroading
-
Stu Olson's Jeep Site says specifically to use 75W-140 for the Rubicons, like BlackYJ said.
So much information out there, and while some of it overlaps, some of it conflicts.