More pronounced rear end "thunk" after suspension update

[oblivionnewtonjohn]

My KJ has a more noticeable "thunk" in the drive-train post suspension update, when placing into gear, more so when it goes from 3rd-4th if I give it more throttle, hard jolt. It's always done this since I purchased, but more pronounced since the suspension update. I just assumed at the time before updating the suspension, it was due to the upper and rear control arms being bad, allowing the axle to move more than usual. I have new Spicer u joints to install today, I did a pre-inspection and do not notice any movement with the shaft/joints as I would expect. I am aware of the 45RFE in some cases, requiring a flash of the TCM to correct hard shifting. But as I said, the suspension work seems to have introduced it more, I did have the differential jacked during the work, curious if I put stress on the joints, possibly failing joints, which made the issue worse?

The other oddity is I seem to hear it lightly in the front also, but more so when putting it into gear.

 

[duderz7]

U joints get used to operating at a specific angle sometimes changing that angle (lift) can help to show their wear. After I lifted mine it wasn't long until I needed new u joints.

 

[tommudd]

You just changed the angles on everything
Could be u-joints, lower control arms weak or upper tri-link
Check the rear CV on the front driveshaft as well since boot goes bad and wears the CV out

 

[oblivionnewtonjohn]

U joints get used to operating at a specific angle sometimes changing that angle (lift) can help to show their wear. After I lifted mine it wasn't long until I needed new u joints.

That makes sense, and I can confirm it somewhat as I had to jack the rear again to replace the brakes, not nearly as "jolty" as it was. Also noticed some play when rotating rear tires. I have the Spicers to install.

Thanks for the reply.

 

[oblivionnewtonjohn]

You just changed the angles on everything
Could be u-joints, lower control arms weak or upper tri-link
Check the rear CV on the front driveshaft as well since boot goes bad and wears the CV out

That's all new. Which leaves me to inspect the rear CV as you suggest.
Odd enough, after jacking up the rear to replace brakes, it's back to it's previous "jolt" only when the throttle is floored.