Need help! Clunking under jeep

So for a few weeks now I've had this clunking under my jeep that I cannot find. It is a repetitive clunking and squeaking noise under 40mph. It only happens when accelerating or decelerating in gear. My jeep is a 97 xj lifted 6.5" with 5 speed trans, np231j transfer case, Chrysler 8.25 rear d30 front, has sye kit. I have changed fluid in transfer case and both diffs. I have also added grease to the rear driveshaft. I removed the front driveshaft and check all ujoints front and rear. I have check all mounts and all suspension for loose bolts. I have done all of this with no luck. Any help will be greatly appreciated.

Engine / trans mounts?
Also - did you grease the slip yoke, or just the U-joints on the rear axle?

I've checked the mounts and they are good. And I have non greasable u joints and a slip yoke eliminator but there is a grease fitting on the driveshaft where the two pieces join and I added grease there. This problem started after driving 80 for about 3hrs.