rear end whirring or growling noise when driving. constant.

could be a pinion bearing, differential bearings, or axle bearings. roll under your truck and look where the drive shaft goes into the pumpkin, if theirs fluid coming out from that area youve got a bad pinion seal and bearing. also pop your diff cover off and change the fluid look for metal particles

I thought the same thing on my 2004 but it turned out that the front bearings and races were so bad I had to have the whole hubs changed. I thought for sure the noise was coming from the differential but it wasn't. I hear this is very common on dodge trucks even more so if its 4x4 and or 20 inch tires.

a whole hub is the only way to do front bearings on a dodge 96+ truck its called a hub unit bearing. generally if its front bearings youll hear the bad bearing when you turn to it. in the case of both front bearings being bad youll feel it in your butt and in the steering wheel and prolly hear some pretty angry noises coming from the front end