yea man i went from 3:23s to a 4:10 and it was like bolting on a blower you gotta drive it around for a few days and let the gears heat up and seat then let that bitch rip, and at 70mph your running abour 2100 rpms, my truck is pretty much stock for engine mods and i run 14.9 to 15.2 depending on weather and stuff so yea get some gears dude