I have a 2007+ Silverado Crew cab short bed 4.8l/4l60 and replaced the transmission about 27K miles ago. I have not done anything to the truck since then. I ordered a 4/6 lowering kit from belltech for my truck. I put the kit on and then my transmission lost 3/4th gear. The transmission guy said the lowering kit shoved the driveshaft in the tail shaft which jammed the sun and sprag gear and smoked the 3/4 clutches. What are your thoughts? I drove the truck about 200 miles with the lowering kit installed.

 

My first guess would be that maybe the flip kit was installed backwards? I think those usually have a location hole that's offset to correct that.
Do the wheels look centered in the wheel well or more forward?

 

Everything looks fine. After I get the truck back from the transmission shop I am going to take a look at double check everything. I am also going to check the pinion angle and clearances. Does anyone have a link so that I can refresh my memory on that?

 

It is entirely possible. I put a cheap flip kit that was given to me on my 2012 crew cab and the pinion angle pushed the rear drive shaft yoke farther in the transfer case. I had to modify the flip brackets to position the pinion ay a better angle and pull the yolk back out of the case.

 

If the transmission shaft is points down 2° then the rear end should point up 2°. They should be parallel to each other +/- a 1° or 2°