my 2015 is smooth as butter. They did change to a single rear drive shaft for the 2015s. maybe they changed it sooner, don't really know.
On my 99 it had 4in rear blocks and a front leveling kit. If i towed with my Gooseneck dump trailer, where the trailer took most of the load, the truck would barely squat and I'd have no vibration. Once the suspension would compresses with a heavy load with alot of tongue weight, truck would vibrate taking off. My take is the u joints are binding a bit.
On my 99 it had 4in rear blocks and a front leveling kit. If i towed with my Gooseneck dump trailer, where the trailer took most of the load, the truck would barely squat and I'd have no vibration. Once the suspension would compresses with a heavy load with alot of tongue weight, truck would vibrate taking off. My take is the u joints are binding a bit.