I'm about to put gears in my truck and I'm trying to find out my axles size what do I need to look for as far as number of bolts for the rear and is there a door code or some thing in the vin I can figure it out with? Thanks for any help.
Jake

 

Depends on what model truck and what gear ratio. You can also look at your door jam on the sticker for the axle code. I have a 06 FX4 with a B6 axle code which is a 9.75 rear end. Another thing you can do is crawl under the truck and look at the tag that is on the rear pumpkin. That will tell you what you need to know too.

Like I said it depends on a few factors but I know for me, 5.4L 4x4 with a 3.73 stock rear end its

8.8" IFS 28/31 spline for front diff (reverse)
9.75" long/short for rear diff