I bought my Dak new in 04,,had that vibration 1 st day..brought it back 11 times the rep and dealer did everything including taking the complete unit out of another truck..Then the rep spoke to another old timer dealer and he said he could fix it and he did!!!..He put 2 hose clamps on the front of the rear shaft and for 150K miles it was perfect.. It just came back !!I at one time a few years ago while I was under the truck marked the clamps ,,and they have not moved.. I tried moving them around on the shaft, and it got worse..they are back to where they were...and vibration is getting worse every time I drive it..I am about to take it all apart..A local drive shaft shop said for $450.00 they will replace all the joints and center bearing and balance the whole set up.....I don't need them to change the u-joints but I'm at the end of my rope with this truck..