if you're doing 25 mph+ in 4x4 you're screwing up...even in heavy snow, there is no reason to ever drive that fast in 4x4.

the handbook says you can go up to 55 mph in 4x4, but you should only do that if you intend to break your truck. so in all reality, not really a concern if there is driveline vibration above 25 mph.

a long lifted truck like the supercab isn't usually prone to vibrations. the length of the drivetrain allows for lower angles in the driveshafts. now if you were lifting a jeep or some other short wheelbase vehicle, the extreme driveshaft angles may cause pretty bad vibrations