Need some dealer help-Vibration

I just had my DC 2012 in for my 30k maintenance and I asked them to review the driveline vibration, soft rear end (I already have 4 leafs) and he did some measurement and came back that since I had oversize tires this was changing the pinion angle and had everything out of alignment causing the vibration.

I explained to the tech that lifts change angles, not tire sizes, I even have the original rims. So I told them to get it down, told them they had no clue what they were doing and I was going to another dealer. Before I got home the tech did some research and found a tsb for my truck and asked me to bring it back. Just so I am sure when I go back nxt week, tire size shouldn't have anything to do with softening my leaf springs and changing my pinion angles causing vibrations.....

Thanks, let me know.

 

you are correct sir