Differentials

Start with AMC, Dane 30, 35, 44 and Chrysler.

What model Jeep is it?

The little tag on the side should tell you the gear ratio. Should have something like 307 373 410 411, etc.

40869-1 is the part number for the diff cover for a Dana 30.
43225 is the part number for the cover for a Dana 35.

I have the parts list saved, but it's much easier to just eyeball the axle to see what it is.

Novak adapters has a gear ratio calculator on their website. Lift should have no effect on gear ratio. 33s won't mess up a differential. Having the "wrong" gearing will either have you lugging a lot from too low a ratio, or revving a lot from too high a ratio. It really comes down to your driving style and what works best for you and your motor and tire size.

Here is a gear ratio calculator I made up some years ago to determine what gearing I should use. I believe you just need to enter in the current gearing and tire size and the tire size you would be going to. I haven't used it in a long while.

It also determines how far off my speedometer would be and what speedo-gear I needed to correct for the change in tire size. That would be different for you though since it refers to a Dana 20 and/or Dana 18 transfer case.

click for image

Being a 4 cylinder automatic I'd probably go 1 gear ratio lower than what it suggests.