i have a 99 cherokee auto 4 wd 3 inch lift when ever i put the truck into reverse ill back up then i will come to a complete stop then i will put it in drive then i get a huge clunk from the transfer case area i cant figure out what it is i checked under neath nothing is loose the tranny mount is new if any one has any idea please let me no thanks

 

You stated that you checked everything. To me it sounds like a bad u-joint, or that you have to high an idle.

 

my idle is really low for some reason when the previous owner did an engine swap due a blown engine cylinder from a bad thermostat. the engine idles at like 500 RPMS and bounces around. is it possible that the u joints could be bad even if i cant feel any any play in them?

 

Ok, if the PO had the engine swapped or swapped the engine himself it could be any number of things. It could be the anything that was bolted to the newer engine when it was installed. Motor mounts could be going bad allowing the exhaust to hit something when torque is applied.
Does it clunk when you start it up and just put it into drive?
You are going to have to just check everything out good and look for anything that looks like it has been rubbing.

 

I Agree with rock toy, check out everything.
about possible bad u-jounts when you dont feel any play in them it is possible, are you checking them while the vehicle is in park and wiggleing the shaft? cause the pressure holding the vehicle from rolling would be enough to fool you. checking your u-joints for play chock the wheels, put in nutral so no pressure is on the shaft. then either wiggle or better pull the shaft and check them. also you said the motor was swapped and new tranny mount was installed. check for loose cross member bolts and for loose or missing bolts in the tranny mount.

 

Mine does the same thing. I just learned to turn my music up if you know what I mean.

 

x2 on a bad ujoint. Jack up the rear end on jackstands, put it in gear (engine off) and try and rotate the tires by hand. If you get the clunk you can pinpoint it's location

 

Slipe yoke @ rear shaft? mine clunks