Speedo calibration with 37's
 

Hate to ask because I am sure this questions gets asked often but I could not find a previous post for the truck I have, only older trucks.

Got 07' with the 5.9, put 37's on it with Edge w/attitude, S&B, and Aero exhaust. Love the truck but the speedo is off. The boys at Edge say that I have to go to the dealer to re-calibrate the factory speedo, even though their moniter gives correct MPH. So went to the dealer and they say they can't do it anymore. Only on older trucks, pre-06??? Is there anyone who knows how to get the factory speedo correct??

You can change it with the Superchips programmer.

On 2007 and up, there are only a few tire sizes that the truck can be "calibrated" to. The largest is a 285. On older trucks, you could calibrate with "revs per mile". This leaves 2 ways I know of to fix the problem. 1. buy a programmer that lets you do this, but since you already have the edge, this may not be cost effective. 2. Buy an electronic ratio adapter that you wire into the speed sensor. See the link..... http://www.abbott-tach.com/era.htm