[zaejones33]

Hello I have a 06 GMC Sierra crew cab 2wd. The front has a 6 inch lift and the rear has 3 inch blocks. Why does my drive shaft slips out my transmission while driving. Do I need to lower my rear someone please help me understand this

 

[Ron Nielson]

It slips out because it isn't long enough for your truck. Something happened/changed with that lift and blocks. How much of the spline is attached to the trans? or how much do you need to pull it out to drop the shaft? You have a 2 piece driveshaft? Has the center support block bearing been changed or altered in position, up or down? Straight line is the shortest difference.