Do you know how much tongue weight you have.My son had the same problem.It turned out that his new Featherlight goose neck trailer put too much weight on the truck.In turn the drive shaft angle was out of specs. The trailer weight was 15000 empty.About 35% of that was on the the truck.He has a 2005 HD3500. GM did shim the drive shaft and put in heaver springs even though the trailer tongue weight was the real problem.He's had no issues since.