Drivetrain Noise

Hey all.
Finally got my rig running reliably, and it starts making noise.
It's a 2000 XJ;
4.0, AW4, 231; factory spec 8.25 with new clutch-plates; D30, ECTED & new gears.
3.5" lift w/ T-case drop & EXTRA add-a-leafs.
31x10r15 BFG MT's.

I'm trying to figure out why there's so much noise under power on the highway. I never do over 65 (which I realize because of the tire size, is more like 70), and yeah, the tires kinda howl. But between 50 and 60, if I'm on the gas at all, it sounds like I've got 40x12.5's on there. As soon as I let off, it quiets right down.
The only thing I can find that's wrong (obviously I'm no expert) is the tranny fluid is about 1/8" too full.
Could it be some other driveline component giving me trouble?

Thanks for your help, ask me anything for clarification.
~C

So a throttle-dependent noise and vibration from the rear at higher speeds? Driveshaft angles and ujoints, gears. What work was just done to the rear, your post just mentions new clutch plates?

The driveline shop that installed the ETCED in the front took apart, and replaced the seals and clutch plates in the rear. I didn't re-gear.
I think all 5 u-joints were replaced last year, plus the 2 front axle u-joints. I have NOT had the chance or change to install an SYE and 'do' the rear shaft, so, maybe that's the issue... I've been toying with the idea of pulling out the add-a-leafs, who knows if that would help.
So you're saying it's probably not anything upstream of the t-case? That'll help me sleep a little better...

I'm going to hazard a guess that with the LP D30, a lift, and a transfer case drop you have some ugly angles under that XJ, and you could be getting some noise from there.

MTs are going to be noisy to start with. I don't know if siping your MTs would help with that. Do a Google search for "tire siping".

I couldn't care less about the tire noise, but the driveline angles... would those cause noises at low speeds too? 'cause occasionally it growls at 0-5mph... which just developed.
I'd have to readjust the spring perches to fix the driveline angles, right?

Honestly, it has been reported that the 2000-2001 are prone to noise when lifted. With the LP D30 your front starts out not so good, the lift makes it a bit worse, then the transfer case drop really aggravates the issue.

I would recommend you get a SYE and loose the transfer case drop. A HP D30 out of a 99 and earlier would also be a nice upgrade, but definitely the SYE.

The rear axle tends to make noises before the front axle does with moderate lift heights. My LP D30 was fine at 3.5"

Noises that are "on the gas" or "off the gas" point toward drive line angles and u-joints.

Check the u-joints and determine the drive shaft angles.

A T-case drop and some rear axle shims may help with rear drive line noise, an SYE will definitely help. 1997-2001 are more prone to drive line noise with lifts than earlier Cherokees.

It's a RHD, so the steering geometry/axle mounts are 100% backwards, so I can't swap it for a HP; I had one, but had to sell it 'cause nobody would flip/remount the tubes.

Since it's an 'on the gas' noise, I'm assuming it's rear, 'cause I don't have a full time T-case.

Shimming... Yeah, I'm not so brilliant. The next thing I want to do is the SYE, so...

Thanks for the help y'all!
If the driveline angles are bad, will it 'eat' u-joints?

Excessive drive line angles will shorten the life of u-joints and cause vibrations.

Check out http://go.jeep-xj.info. GoJeep has a RHD XJ and has lots of tech info. He shows how you can build a track bar mount for your RHD. You may be able to adapt a HP LHD D30 fairly easily.