While driving there is a "rore" when the gas pedal is pressed down. When you let off, it stops. I'm not sure if it's coming from the rear or if its coming from the trans. Its been doing this for about two or three years. What could I do to fix this?

 

Sounds like a classic U-Joint. That long of vibrations I would assume that it would be comming from the front. Although a CV joint could be to blame. Eather way this is were I would go for sure.

Other things to look for would be a bad bearing in the T-Case, Rear end, or Front end. If anything is leaking then this is where I would start.

 

Does the sound you hear,could coming from under the driver's seat? If it does it could the large roller bearing inside the overdrive unit. This as been a problem with 44RE and 46RE transmission in jeeps and I am finding the some problem in dodge trucks.

 

U Joint. Could this also be the problem when I shift into gear, most noticably into reverse, there is "clunk". Changing them anyway. Can't be that hard and not that expensive. 10 years old time to change. Thanks for the responses.