I bought my new Ram 1500 5.7 with 3.55:1 rear end, and then upgraded it to 3.92:1 rear end gears. Now I need to recalibrate the speedo. As I understand it this is all electronic now so no need to change the speedo gear in the trans. Has anyone done this or is this just a simple trip to the Dealer to have them change the program showing 3.92 rear end ratio?

Dan

 

The only reason to recalibrate a speedometer on these trucks is a tire size change. The sensor is in the rear axle and reads axle rpm.