As I understand it, the older 5 speeds (pre 98) are pretty weak. Then, the NV5600 (New Venture) came on line in 98 and had some input shaft issues that were corrected in 00. Dodge used this tranny until 2005 and it has a good reputation for reliability.

In 06, they switched to a Mercedes unit that is bulletproof. I've got nearly 50k miles of towing with no issues. The Cummins Ram boards have plenty of guys who went 150k on the stock clutch.

The automatics are actually weak up until 06 or 07, I can't remember which, and are to be avoided. They are the units that gave Mopar that bad name as far as trannies go.