M923a2 clanking grinding noise from under cab? Transfer case or U joint?

[Oldworldtenacity]

Yes,it was heat sensitive.The transmission tailshaft moved upward 1/2 inch after loosening mount bolts.It's binding/preloading the upper bushing.Loosen the bolts and insert a piece of rubber between cab floor and mount(I used a leather glove,all that was available at the time) for temp repair to verify issue.The contact was transfering all the driveline noise,squeaking etc sounded exactly like yours.

Well, you were right!!! After all of this time thats went by, thats exactly what the problem was. However, Fleetpride had a different take on why the transmission bracket was making contact. They said it looked like my cab was tilted back slightly, so they unbolted the two rear cab mounts and said it looked like they were installed upside down, because all they did was reverse them and it gave the cab the space it needed to clear the brackett and now no more drive train noise is being transferred. So I guess some moron put the cab mounts on upside down when they were retrofitting these trucks with these newer cabs and caused me a whole lot of grief over this pesky problem that no one could pinpoint.
Thanks much for chiming in 146APF. Fleetpride admitted they didn't catch that until I suggested it after your post on here. Thanks again!