My 04 Dak club cab 3.7 V6 2 wheel drive auto..I bought new , and it had a vibration from new in the drive train around 30 mph unless driving thru that speed..Almost to a point of the lemon law complaint ... they replaced everything other than the trans,,,Finally a service manager from another dealership..told the rep that he knew what to do..he balanced the rear ( 2 piece shaft )with two large hose clamps..said it was in the service bullitins ,,and it worked perfectly for 150K miles..and it just came back..same vibration ,, clamps are still there and tight ..now what to do.. Truck looks and runs like new other than that .. and I can't buy a new one at this time.. Help

if the 2 piece driveshaft was out of balance from the factory, and the hose clamps helped balance it, then I would look at your driveshaft.

did any weights fall off? are the U-joints failing? is the rubber bushing that holds the carrier bearing starting to fail?