:o I just re-read the post and this time saw that it's for a 6400 truck.
Being an open driveline,the same concept applies,but it's a lot easier. All you need to do is chock the right wheel,jack up and block the left rear wheel,leave the truck in neutral and mark the driveline,the inside of the tire and the brake backing plate. Now,turn the driveline and count the number of revolutions the driveline makes for a full revolution of the tire. That's your gear ratio.
Speed
