when it was implemented in ‘59 or so, there wasn’t the high powered driveline combos that started showing up in ‘62. I’m sure many a neutral drop of the early Max Wedge cars necessitated the increase in size of the pinion shaft and carrier bearings.
and personally, I have seen axel shafts twisted at the spline end, gears stripped from a ring - pinion and once the bearing caps blown off, but I have never seen a pinion shaft break
