Be watching this thread. First I read on search, lol.
Little rumble 2wd, same in 4 on gas, more when letting off.
Least now I know I can remove D-shaft to diagnose shaft/ujoints or axle problem.

 

Do a search for diagnosing wheel bearing hubs. I had a lot of similar sounds and when I changed out the bearing hubs....sounds all went away.
Cheap fix and with that mileage, probably needs to be changed anyway. Should only take less than an hour per side to do them. Good luck!

 

Usually wheel brgs can be determined by going down hill in N, swerve side to side, if turning right left wheel will have higher load and make noise if bad.

 

Anyone reading this with similar probs... If you remove the front shaft yourself - I do not recommend putting it in 4wd at all (especially Full Time) because you might damage things. Pretty sure I just f&%ked myself right out of a fairly new transfer case replacement this way - and the rebuild part is more expensive than getting another used case. I'm starting a NP242 junk yard, yay. Live n learn.

Frustration central.