You guys seem to have all the answers one could ever wish for, so let me toss one out. Just put a 14 bolt FF 4:10 eaton under my trusty Chevy, but.. seems the speedo is now 20% off (had 3:54 gears before). When I went to see what color gear I had in the x-fer case, it wasn't a gear, but a sensor! electronic speedo! Does this require DEALERSHIP REPROGRAM (boo hiss!!!) or is there somewhere else a tweak can be made? Thanks!