Thanks for replys. I might exhadurated a bit about the rpms, but they are still very hight - no less than 2700rpms at 60-65mph. I checked my tires, I have dully 225/70/19.5 on that truck. I couldn't find the axle code and vin tag on the door is pretty washed off so I couldn't read axle code.

Where can I get some gearing for my rear end?