Low rumble when loaded in 4WD

1991 1/2 ton 350 sub.

I get an intermittent low rumble or vibration when going up or going down steep grades in 4WD. Most often is in 4-Low but sometimes in $-High. Thinking I have a stuck U-joint on the front drive shaft but want to hear if any others have similar experience before investing the time in the repair.

Lot's of good info on the site, thanks for all the help.

Monte

More than likely the front shaft needs to be completley rebuilt.there is a little ball and seet in the double jount that is probably the culprit!!

good luck

Gary