I have just changed out the rear drive shaft u joints and that did not fix it. We did disconnect the front shaft and drive just with thte back and the problem was still there. If you hold the rear shaft out disconnected from the diff, but connected to the transfer case there is some rotational play, about 1/4" each way. We thought that since the ujoints were new then something must be going in with the tcase.
Should I try to run on the front shaft? Will this prove if there is slack in the tcase chain?