http://www.certifiedtrans.com
This is an extremely common problem in 4 wheel drive trucks, especially Dodge's. The driveline will vibrate for various reasons and either crack the adapter between the transfer case and transmission (overdrive housing). OR Break the transfer case, as it did in this truck.

Driveline vibration is VERY EASY to misdiagnose. Ujoints seize up and vibrate long before they grind themselves up and get loose. Bad Ujoints that have seized will feel tight in the truck and will get judged as "good".

The only accurate way to check a suspect driveline is to remove it from the truck. If in doubt after removal, we suggest taking it to a shop that specializes in this kind of work.