About 4 months ago i had a 6 inch superlift with 35" pro comp tires put on my truck!! A 2005 crewcab 4x4 6.6 turbo diesel with the Allison transmission. The trucks great but about a week or so ago i engaged the 4x4 and i started to get a vibration running thru the steering wheel at low speed trying to get thru some deep snow. this only happens when the truck is in 4wheel drive. Does anyone know what this could be caused from! Some guys are saying something about a driveshaft.
Need some help!!!!!!

Some lift's require a different front driveshaft, (or CV Driveline as I have read).

Search "vibration" or "driveshaft" in the Suspension & Steering section.
Nor-Cal Nick has posted about this issue.
Here's one thread:
http://www.dieselplace.com/forum/showthread.php?t=285373&highlight=lift+drive+shaft
http://www.dieselplace.com/forum/showthread.php?t=341043&highlight=vibration
http://www.dieselplace.com/forum/showthread.php?t=315167&highlight=vibration