Have had a vibration at pretty much 25mph and higher for a while now, had my primary and my spare driveshaft balanced, still a vibration. Wheels re balanced, still vibration. New carrier bearing, still vibration. Let off the gas it would sort of disappear. Drove on just my front axles in 4high with no rear driveshaft, no vibration. Finally had enough, and was going to dig through all the suggestions and items to check from other posts on here. Yesterday, removed that rear driveshaft again and noticed the differential pinion nut had become unstaked and was loose. Had to go buy a .30mm socket to tighten it up. Torqued it to 145 ft lbs per the shop manual, restaked the nut. Reassembled everything, Took for test drive on the highway, no vibration, problem solved. It's like driving a new truck, so happy now. BTW my truck has over 430k miles on the original engine and just keeps going and going.

 

Glad you figured it out, I will remember that if I ever get a vibration similar.

430k Miles eh? Post some pics of the rig!

 

 

Nice looking truck!

 

Looks like youve been taking care of that truck!