The bearing, locking ring, and retainer are the same for 28 or 31 spline axles. The only difference between the 2 is the axle seal used. The 31 spline axle uses a seal with a larger ID and a thin sleeve that is pressed on after the bearing and ring to increase the axle OD to accomodate the larger ID seal. Ford did this so the larger splined end of the 31 spline axle wouldn't damage the seal surface when installing the axle. If you don't have the thin sleeves (alot of people don't reinstall them as they are easy to damage when removing the bearing), use the seal for a 28 spline axle and be careful when sliding the axle end thru the seal.
Using the correct 31 spline seal without the thin sleeves on the axles has caused countless leaks and headaches, if they are gone most mechanics would never realize they were missing.
Just FYI, If the sleeves are still present, the easiest and safest way to remove them is by gently heating them up with the axle standing up on the splines, they should drop right off. Heat them up and drop them back on after the seal and ring are pressed back on.
Hope this helps, John
