Death wobble is all in the front end. I have no wobble all my suspension is new including all the steering.
both axles rebuilt with all new bearings, front axle u-joints,front hubs, rear wheels bearings, yukon gears and LSD's, $1900

 

Update:
Drove it with just the front shaft and no vibrations all the way up to 70 mph.
Had the rear shaft rebalanced. It was pretty good but they spun it to high rpms and it needed a little better balance. Reinstalled it and it still has the vibration. Next is I will be removing my 4 degree axle shim and installing a 3 degree axle shim from Tom Woods to put me just below 2.5 degrees below on my pinion angle. I have narrowed it down to a bit more axle wrap with the new gears so hopefully this fixes it. Will update after my family vacation. Thanks

 

Subscribing to this to see how it turns out.

My thoughts are you're not going to get "axle wrap" in an XJ unless you put in a tricked out 350 Chevy or are pulling stumps.

Even if axle wrap were a possibility it would not be present at essentially steady state highway speed.

And even THEN if your eyeball measurement is correct your pinion angle is well WNL.

I would get it up on a lift and watch at 70 MPH but I thinking you're gonna be putting in a new pinion and carrier before you're done.

Did you check the runout on the rear wheels and check the alignment of the rear relative to the front? Is that an 8.25?

 

Hi. The carrier and ring and pinion are new. Run out was checked on both axles flanges at the drums also both rear yokes ( on axle and transfer case) alignment front to rear is dead on ( had it done after the suspension was installed) so no crab walking. I have 3 videos of rear axle showing a decent amount of axle wrap while on the gas all the way up to 70 mph. The axle is a 8.25

 

Considering none of the vibrations were present before yhe gears were done it has to be related to anything the gears would affect. So anything outside of that is not going to be the issue.

 

OK so time out--

Is this vibration ONLY on acceleration? Again, at steady state any axle wrap should be gone, and if so, the vibration as well. If it's vibrating when your foot's off the gas then it definitely ain't that.

Define "decent amount". According to your posts that seems to be ~4.5 degrees, but is that only at maximum acceleration?

If "axle wrap" is truly the issue (and I don't think it is) IMO you'd do better putting in traction bars that trying to fine tune a degree or 2 in a highly dynamic situation.

 

They are also "different".

 

Yeah the Vibration is only present while accelerating above 55 mph. When I let off or just cruising I have no vibrations but a soon and you start to accelerate you can feel the vibration and clearly see the axle yoke raise in my videos. I find it pretty crazy how sensitive the xj's are to lifts. I thought I wouldn't have any of these issues with a sye. I think my vibration is on the lower spectrum of vibes from the examples I have read from others. If the new shims don't fix or at least make a noticable difference Ill have to revisit the rear end (gears and carrier as suggested). Thanks for the input so far I do appreciate it.

 

As far as axle wrap on acceleration I can see it clearly go above level on acceleration. Wish I could measure it while driving lol. Hard to tell but I would say 3 degrees but watching a video only gets me so far amd can't just eye ball it.

 

I would also check the clearances myself. Ring/pinion backlash .006. Pinion preload about a pound (without the ring in, so you'll have to fake it a little). Yank out on the axles, there should be the tiniest amount of play (.005 if you were measuring at the side gears). My WAG is that something is a little too tight, or a bad bearing (they can be noisy out of the box).