[Evildriver-3]

Is there any damage to the driveshaft? also under power or just in that mph range or does it stay constant after that mph

 

[mike_wiz]

getting the driveshaft lengthened is not that much $....I found a place here who will extend one and balance it for $80...just My $.02

 

[WyzGuy]

You may need to use shims to get the pinion at a better angle. I assume the kit you used to lift the truck either had taped blocks or shims for the springs. It just may need a few more degrees of tilt to reduce vibration.