I'm changing tires from 245's to 265 BFG's. Is there a speedo gear that will work with these or do I need to get my PCM reflashed? If there is a gear, how many teeth? Thanks all.

 

Dodge uses an electronic sensor that is connected to a gear in the tailshaft. You can replace the gear and turn the sensor housing to compensate for most tire sizes. The best place to start is a speedometer calibration shop for the proper gear size.

You can also purchase aftermarket electronic recalibration devices from most 4X4 and off road shops. I use that option because I change tire profile and size for elk season and then back for normal driving. The electronic box lets me just select the setting and go, without having to hop under and screw around with the speedometer drive system. But, it is about $200 versus maybe $10 for the gear and fooling with the grease.