Hi all,
Have had this 97 XJ for about a month or so. 155k miles, stock, auto trans. I have a thumping noise that is rhythmic and speeds up and slows down based on vehicle speed. Sounds/feels like driver side frontish area. No change in volume/pitch noise while turning, or while in 4wd. No grinding noise present. There are clunks and such however they appear to only be when hitting bumps. I have replaced driver side u-joint, front driveshaft-front u-joint and driver side wheel bearing. No change in noise. I have searched the forums and to be honest probably missed it, but not sure where to go from here. Thanks in advance for your help.

 

It could be loose flexplate to torque converter bolts, cracked flexplate or bad torque converter.
There is an inspection plate on the bellhousing of the transmission, you can remove it and make sure the bolts are tight and inspect for cracks.
Also, check you motor mounts and transmission mount.

 

Have you greased the slip joint on F drive shaft?
Might consider joints and centering ball on Dcardan joint. Kinda tough to take apart, not bad going together, just mark relationship of pieces first.
Check and or change axle fluid.