HeavyHook

Hey all, a new member here. Did a little research on here. Have found out that the 99 XJ I have is suppose to have a D30 High pinion, reverse cut front diff.
I also have a 2000 XJ that as I understand the research, should have a D30 Low pinion standard cut.

Here's my question... My 99 has over 260k on it while the 2000 has only 152k on it. So I picked it up as a donor vehicle (smacked on the passenger side).
So now I read here that mine is a D30 HP R cut, while the other is a D30 LP S cut.

Can I do a complete front diff swap...disc to disc. What issues will I have. The rear Diffs are a direct swap, so no issue there. Was looking at doing this today or tomorrow, all info is appreciated.

jwilson2598

Yep, it's a direct swap, everything should bolt right on.

HeavyHook

After yet more research, I'm lead to understand the HP is more desirable over the LP D30.
Then if this is true. I should look at repairing the shuddering/clicking in my D30 HP ???

CMMC

Just do the swap and while you have the HP out you can take your time to diagnose and fix it. You will experience a difference in drive shaft angle when you do the swap but any effects should be negligable.

HeavyHook

Currently the XJ is at OEM height. Is it the general thought that I should get NO vibrations via driveline angles. And your opinion is the reverse cut D30 high pinion would be more desirable to keep/diagnose and reinstall?

HeavyHook

Any other opinions and or advise...?

Jamie57

Nope. Do the swap. Keep the 99 HP axle and repair it while it is out of the vehicle and replace the LP axle when you have it fixed.

It's really not that much work and for a temporary fix you should be OK.

If you NEVER plan to 4 wheel in rocks and really ruff stuff you could axtually leave the LP in.
It's not that much weaker and the clearance loss is only a couple of inches right at the yoke.
They have put those (LP) in every year of Grand Cherokee since they started making them.

Just noticed where you live. Your not going to the Badlands with this are you? If you do Take pics! Ive got family out that way I want to visit some day.

HeavyHook

Ok gang, update....

After jacking the XJ up at all four corners, and with an assistant. I don't think the problem is the front diff. I feel (in the drivers seat, floor area), what I can best describe as "chatter". Viewing the axle U-joints and driveshaft U-joints, along with a touch/feel inspection. The front components seem good.

Now, I do have 4wd in all functions. Forward and reverse. What's getting me is, in any gear and any 4wd function position, with light throttle everything is fine. If I go medium to heavy throttle, then I get this chatter, almost banging. It kinda seems almost like it's slipping in and out of 4wd.

Finally, all this happens in any 4wd position ONLY !!!! When in 2wd, the thing is smooth, in all gears. Oh and I did inspect the motor and tranny mounts for play. Seem good.

Folks, I'm in need of some ideas. My repair manual is vague in regards to T-case problem solving.

HeavyHook

Anyone...

I know I'm a Newby here, haven't made alot of contacts yet. But I'm kinda counting on the CF too come trough for me with some ideas.

HeavyHook

...

bsmith97xj

Is the Jack stand under axles? If not the chatter vibration is cause the axles are hanging.

HeavyHook

The XJ was supported at all corners on jack stands. The chatter/shuddering can not be duplicated.
When dropped and field tested, is when the noise/feeling through floor happens!!!

HeavyHook

Crawled under it again today, it's a NP242J T-Case, in my 99 XJ Sport. Are they prone to chain slippage, or other suggestions...

HeavyHook

...Hello

Red82

Are you actually moving the vehicle in 4wd or just giving it gas while its lifted off the ground? If you're on dry pavement that and driving it that could be part of the reason. I'd try changing the fluids in both the diff and tcase and take it from there.