Who knows what size u joints are in the driveshafts of my '91 XJ? I just picked up a Ford 9 inch and the u joint in my spare rear driveshaft fits perfectly in the yoke of th 9 inch. I thought I read some where that the XJs have 1310s. Also, did all XJs come with the same size u joints in the driveshafts?

 

1310s in front and rear. Guessing you got a 9" out of a car cause all the ones I've used out of trucks use a 1350.

 

The code that was on the dif tag told me its from a 63-72 F100. The axle width is the same as an F100 as well. It also said that it came with 28 splines but it has 31 splines. So Im guessing who ever owned it did some mods to it. The tag says it has 3.25s but Im not sure. Ive opened it up but the only markings I could find were on the carrier which are "C6AW 4205-B" Any idea what that means?

 

yeah, my 78 bronco 9 has 1350. so not sure why yours has 1310.

but spin your ring gear and look for the number stampings on the edge. the last 4 digits is your gear ratio. divide the first two with the last two numbers and you'll have your ratio.