2000 XJ 4WD 4.6L NP242 here, currently stock height but anticipating a 5.5" lift within the next couple of months. Things keep happening that make me want to take the steps of my build in a different order than is ideal.

Searching gave me some good info, but I couldn't find a definitive answer to this question. My rear axle currently has 3.55 gears. Suppose for whatever odd reason that I wanted to replace my LP D30 up front with a HP D30 out of an older XJ, but the replacement had 4.10 gears already in it. Let's forget for a moment that the front drive shaft would bang into the downpipe with that configuration.

Would there be any other negative or disastrous consequences of running the mismatched gears IF I never put it in 4WD? I know trying to use 4WD would result in Serious Damage. But what if I always left it in RWD until I can get my rear axle set up and installed?

Along those same lines, could I run it without a front drive shaft, or would doing so damage the NP242? (Again, assuming that I taped a big "NO!" sign over the 4WD shifter.)

My gut tells me I could run this setup indefinitely with no problems if I keep it out of 4WD. Am I missing something?

 

Remove the front driveshaft.

Don't run mismatched axles with the front driveshaft still intact, doesn't matter if u don't put it in 4x4

 

X2. Pull the shaft. Won't be an issue

 

Okay, sounds like a plan.

But why? If the front drive shaft isn't turning, why would it matter if it's there? That's the part I'm not quite understanding.

 

it still spin because when u move. The front wheels turns the gears inside the housing, which obviously also turns the driveshaft. Inside the t case, the chain is spinning.

 

It can start a fire. Ask my little brother

 

Well since we don't know your brother can you elaborate?

 

Pull the drive shaft but what size tires are you planning on running? Regearing an axle to 4.10s is kind of a waste of money.

 

I'm not regearing to 4.10s. This is a bit complicated (which is why I didn't post it initially), but now that I have my answer, let me see if I can explain:

My Jeep currently sits on a low pinion D30 front and a D35 rear, both geared 3.55. I have no intention of wasting money on either of them. I want a high pinion D30 up front and a Ford 8.8 in the rear.

I have a set of 5 rims that I got an amazing deal on, and they already have nearly new 31s on them. So, since I didn't want to toss out a perfectly good set of rubber, I figured I would run them for a while and then step up to a larger size when those are toast. They may look a little strange with my lift, but I'm not too worried about it.

I figured 4.10s would be right for 31s, and since I was replacing both axles anyway, I just searched until I found them already geared to 4.10. The rear, which I picked up yesterday, is a limited slip 4.10 8.8 out of an Explorer, which was surprisingly difficult to find. The front is a HP D30 out of a 2.5L 4WD XJ, which came from the factory with 4.10 gears. It also wasn't easy to find, because who the hell bought a 4-cylinder 4WD Cherokee?

Both my front u-joints are shot on my existing D30, and the differential seal at the drive shaft is showing signs of leakage. I know it's probably lazy of me, but I really don't want to put any work into that axle only to pull it within the next couple of months anyway. So I want to set up the HP D30 and run it disconnected until I can get the 8.8 set up for the rear, at which time I'll also be installing frame stiffeners, the lift, SYE and steering upgrades all in one massive undertaking that makes my savings unhappy.

When I use up those 31s, I may regear for larger tires at that time and put a selectable locker up front. But this way I can at least kick that can down the road so as to postpone the expense of regearing when my bank account is already going to be screaming from all these other components.

ETA: I should make it clear that I'm not building a rock crawler, but a bugout vehicle for hurricanes and moderate street flooding. I want to be able to handle mud and water and negotiate road debris. Eventually I want to be running Kevlar tires and a full set of skids. While it will see mostly in-town use when there's not an emergency condition, I'll probably go play in the mud some on weekends. But this thing doesn't have to be able to climb a mountain.

 

Sound like a plan. Just leave the front driveshaft off the jeep until u put in the 8.8

 

those axles are fine on stock tires. crawl before you walk. only change axles/gears when your height and tire size is figured out

 

Sounds like your on the right track. Didn't know you already had a 4.10 rear axle.

 

Stock tires and rims would look ridiculous on a 5.5" long arm lift.

 

The gear oil in the front axle got so hot it within 45mi. smoke was pouring out of the axle seals and you couldn't touch the housing.

 

WTF did he do to cause that??