I am having my Ram 1500 with 4.7L and 5 speed switched from stock 3.55s to 3.90 rear end gears, does the computer compensate for this somehow, or will I have to have something done to correct my speedo reading? All help appreciated.

 

You do not have to do anything for the speedo with a gear change in the 3rd gen Rams.

edit: I've read its recommended, but not 100% required to have the dealer flash the computer for the pinion factor, though it will not affect the speedo and I know of many many guys who havent had it done.

 

Your pcm does have to know the correct gear ratio and tire size to calculate vehicle speed. You can take it to a dodge dealer and have them change the pinion factor.

 

Thanks guys, much appreciated info.