Originally posted by DodgeTorqueWagon
Paul,
Welcome to the TDR! There's SOOO much great info here...
In 2001, the 6 speed was only available with the HO - even according to the Dodge Product Guide I have here. I think there were a few trucks in 1999 that were standard output engines with the 6-speed.
The NV5600 6-speed is substantially larger than the NV4500 5-speed. The clutch may not withstand as much as far as engine upgrades (more power!), but overall it is a stout transmission. There have been some synchronizer issues, especially when cold, that were covered under a TSB. Might not be covered at 100k though. If it had an issue it may have been done already.
One advantage of the 2001 may be rear disc brakes if it was a later build - I know mine were vastly improved over my '99 and '00 drums. Anything can be fixed on them of course - lift pump, clutch, etc. Hope it works out for you...