I seems as though this subject has been beat to death, but in all of my searching I can't find any problem that exactly describes mine. I have a 1997 Jeep Grand Cherokee Laredo. It has a 249 transfer case-quadratrac, 4.0L engine, and no modifications. I am experiencing a vibration/rub under light load over 30 mph, it goes away if I "punch" it, or release the accelerator. As I go down the road I seems to be coming from directly under my feet on the drivers side. The noise can be described as rub-rub-rub-rub in a monotonous rhythm.
I went underneath and checked the u-joints and shafts, along with the transfer case. The only play I found was in the front output from the transfer case. The shaft can move radially slightly and a little more axially. I am not sure if this is normal, because the rear shaft is nice and tight. I unfortunately did not have a chance to do this in neutral, so my attempts may have been wasted. The u joints seemed to be good, but it was hard to tell at the double-joint going to the front axle. I am inclined to rule out a T-Case bearing only because the noise/vibration happens under certain conditions. I am stumped right now and any help would be appreciated.
Adam