2 piece steel stock DS ftmfw. I've had mine up around 130 no problems as have many many others. I know nonnie has had his well over 150 mph.

 

ha before i even had my truck tuned i took out my drive shaft (2 piece from ecsb) and put a new carrier joint and had it balanced....now at 120+ i dont feel any shake or vibrations.....oh and maybe a noob question but do you have to have a posi rear to go to a dyno to spin both rollors?

 

is your truck lowered at all? That's probably what caused the vibrations. Mine was dead smooth up there.

 

you askin me? after i lowered mine i got a little vibration but i changed my carrier and had shaft balanced and it fixed it.