[Mike Bontoft]

Mark Williams machined all of my HD stub axles, They are expensive but the best. We even had them machine 19 spline axles and I don't remember ever breaking one on a Cobra. We did have some applications that could break them but it was never on the spline. They would shear off at the threaded portion, we fixed this by eliminating the threads and using sweat on collars.
The next weakest link then becomes the outer stub shaft.
The later Powerlocks, 30 spline, one piece side gears, metric/LH case bolts were the ticket but became very hard to source. The Auburn Pro 30 spline worked well with the correct additive. Main case needs to be ground on some.
Mike