gingerfold:
Kirkstall was regarded as THE back axle in the 1950s / '60s for the “loose axle” market and for the chassis assemblers rather than the fully integrated vehicle builders. As Pete says the theory, and practice, of hub reduction was less strain on the half shafts. Albion axles were hub reduction and very well regarded.
I still don’t know how I managed it, I once snapped a half shaft on an Albion reduction axle. All I was doing was easing it forward on the weighbridge at the old Ripon Gas works. 
Double drive, reduction hubs, and your correspondent snapped a halfshaft, Old Fred Chappell swore at me…a lot. 