If I remember correctly there are 2 options for big bolt pattern axles.
1. Axles for using stock abody small bolt pattern backing plates and drums (slotted to fit big bolt pattern). Using a stock small bolt pattern housing width will result in a stock small bolt pattern flange to flange overall width.
2. Axles for using big bolt pattern backing plates and drums (already at 4.5" big bolt pattern). Using these axles with a stock width small bolt pattern housing will result in a slightly wider overall axle flange to axle flange width. Wider than the stock abody small bolt pattern rear end. I can't remember how much wider off the top of my head right now.
The reason for this is the drum backing plate offset is different between small and big bolt pattern rear ends. This makes the distance between the bearing and the axle flange longer on the big bolt pattern rear ends. Also If I remember correctly the register on the axle for the drun is a smaller diameter on the small bolt pattern axles.
I think you can narrow the housing and shorten the spline end of the axles by the offset amount and end up with the same overall axle flange to axle flange width as the stock small bolt pattern 8 3/4" rear ends. I think Dr. Diff offers the axles both ways.
If this isn't right please say so.
