QuickNDirty

So I've had the XJ long enough to know what I would prefer to be different about it, and one of the main things is the gearing.

Currently I'm running a 93 XJ 4.0/AX15/NP231 with a D30 up front and Chrysler 8.25 in the back at 3.07 ratio on 30" MT tires.

It's a pretty awesome critter and gets me where I want to go, but 3.07 ratio makes going slow in 2HI/4HI on crappy terrain a bit of a chore, and 4LO is a little too slow.

There are three things I want to accomplish:
1.) first gear speed to be ~4MPH at idle, definitely less than 6MPH
2.) Some extra torque so going up steep hills in 2HI/4HI is possible without baking the clutch or beating up the jeep by going too fast for the terrain.
3.) Able to go 72-75MPH under 2500RPM.

With 30" tires and a 4.10 gear ratio I get pretty close to that judging by http://www.grimmjeeper.com/gears.html which seems to match reality a bit.

If you were me what would you do?

dans98xj

If you are looking to get back to stock the 4.10's should be good. But If you do any towing or you are looking to get bigger tires in the future you might want to just go to 4.56 of 4.88. And if changing gears is not really in the money right now you could look for a set of axles from a 4 cylinder and that would give you 4.10's. Or you could swap in an axle set from a 6 cylinder auto and that would give you 3.55's, it would be a little better than the 3.07's. From reading you post again and looking at the link you might want to look at 3.55's if you stay at 30" tires.

XJwonders

Go 3.55 from auto XJ. I had 3.55 on my 99 ax15 on 31" tires and it was excellent combo.

diskman

Yep. 3.55 is where you need to be at. Easiest and cheapest is to grab some complete axles from a junkyard or Craigslist. I ended up driving 500 miles for my set of low mileage 4.10 axles. I gave my 3.55s away. I spent $300 for the axles, another $100 on seals, new brake hardware and paint. Regearing was over $2400 for both. ugh.

QuickNDirty

That was kinda my plan. I don't have any problems so far with the 3" lift and 30" tires. I can crawl over cut down trees and through some nasty ruts and stuff without banging anything on the bottom. 3.55s would probably work pretty well. The reason I want my numbers like that is so I can go slow enough when I need to without dropping to 4LO, and also drive close to the speed limit in places where folks will run you over if you aren't doing 10 over. Jack of all trades kinda thing. I wonder if my mechanic/warehouse guy would trade me gears?

All this might be moot, though. Yesterday when I cranked her up to go home I heard this god awful whirring that I thought might have been a pulley bearing or something but when I got home I checked the oil just because and found some fine metal shavings on the dip stick. I don't think they were there the day before when I gassed up and checked.

Oil pressure is fine (40ish cold idle, 15ish at warm idle, 40ish when cruising) and the oil level is fine. I'm going to pull the pan off tonight and take a look at the bearings. I really hope I'm not screwed. This engine only has 89k on it. Maybe it's the timing chain eating away at the cover or something.