I've got a 99XJ 2 door with 130K on it, a new engine, new radiator, and all the normal maintenance kept up on. It's on 29" tires with a garbage Rusty 2" lift from the previous owner that rides like the wheels are bolted to the frame. Gearing is stock, auto trans. D35 rear axle.

I've had it for a couple years now and the girlfriend and I use it for solo overlanding, driving 1000-2000 miles on the freeway, then loading it to the max GWVR with gear and water for 7 days at a time in very remote places. We don't wheel on purpose, just to get to get past obstacles. It's surprisingly capable as it is, but I feel like a little more room under the pumpkin and a locker would make a big difference in both capability and safety for us. The biggest issue is always sand, we've had some pretty sketch moments driving fast in 4 low where if I had lost momentum I'd probably still be there!

Up until now I just didn't see the benefit in dumping serious money into it, but we were 2 days away from wheels up on a major trip when the front diff exploded on the freeway (huge BANG, then couldn't move in any gear with traffic screaming around me) and it made me realize that we've been rolling the dice harder than I thought, and I no longer trust the rear D35 either, so I'm def gonna have both diffs rebuilt, but considering the cost of that and that labor is basically free for locking and adding stronger axle shafts at that point, I'll probably do that as well to get us more reliability and capability. Of course at that point it seems dumb to go back to stock ratios and put all that work under a suspension that I hate. So it seems like now is the time to regear, lift, and put on some bigger tires, all of which adds up to some pretty serious $$$.

I'm limited to 31's because in my case I have to put the spare in the back (rear carriers steal too much payload and my roof rack normally has small boats on top). I'm also VERY concerned about getting the gear ratio right for best MPG on the highway. We drive 65 here, 55 in Mexico! My locker choice really depends on what is going to work best on sand and ice. Sand is more important than ice.

So here is the current plan:

4:10 regear
Stronger front axle shafts
stronger rear axle shafts or a 8.25 swap (I'm not as freaked out about a D35 upgrade as some people, same tubes on a 44 right?)
3" OME lift, shocks and springs with an extra spring in the rear for the weight
new cheap 15" wheels and 3.5 backspacing
31" BFG KOG2's
Rear locker??? Was gonna go with an OX but I'm open to a lunchbox if it's not gonna be sketchy on snow or ice? Anyone with real experience with both?
LSD front? waste of money, overkill?
Stronger Adjustable lower front control arms? overkill or a good idea? (already have a track bar)

Anything else I'm not thinking of here? Anything I'm thinking wrong about? Hoping for feedback from people who have actually done something similar, not just repeating what other people say. I appreciate the help. It's a big investment and I don't want to screw it up.

 

So be gone with the D35. Even a bolt on C8.25 as is will be better off for your use. Prefer the later year C8.25 because they have better shafts - i dont recall the year split exactly because this is just off the cuff but other will cut in that year split with ease.

So for 31" tires i don't think you'd really need a re-gear honestly. My overland/family wheeler is 4.88's and 33's locked front and rear but i have spin free hubs up front. The gearing i have doesn't make for great highway fuel usage. it definitely eats it up around 2300rpm and 70mph. I think your best money investment is an (8.25 and) locked rear (I've had excellent experience with grizzly lockers through multiple axle setups). If you want a little more and still gear change maybe even an 8.8 swap and those can be found easily with 4.10 gears and LSD. Some type of setup so you can air-up tires (like a milwaukee air pump) would be a good idea as well

 

Get rid of the junk Dana 35 and put a Chrysler 8.25 in, and a lunchbox locker works great in the rear, even in snow and ice. Also what actually happened? If your front axle blew up you would still be able to move in 2wd.

 

all the parts are still spinning in there all the time, so drivable just depends on HOW things blow up. In my case there's shrapnel in there jamming what's left of the gears.