Big bearing vs Small bearing, is the axle dia. the same for both?

[reamer]

What are the true advantages of a big bearing diff?
also, a 28 vs 31 spline axle, are they the same dia. also?

 

[garberz]

Big bearing diff holds a larger OD axle bearing. More GVWR.
31 spline is a larger dia than 28 spline in the critical area where the wheel bearing rides.
1.562” 31 spline, vs 1.377” 28 spline.

Mark

 

[Apogee]

The 31-spline axles are about 30% stronger than the 28-spline axles in torsion and run larger bearings (ID and OD) which make them stiffer for less deflection outside the bearing.

There are were two different axle diameters/bearing ID's used, Ø1.563 and Ø1.531 for SET20 and OE sealed ball bearings, though if you count the aftermarket sealed ball bearing options, those are available with either ID.