Thanks for your replies, wow I would not be happy if the gearbox split in two
I just pulled the broken shaft out again and noticed that the bearing for the
pinion shaft has been destroyed also. That would explain why I needed to shim the drive yoke
the first time it broke. Maybe that caused the heat build up that distorted the plastics?
Hmm, not sure why the UJ would get so hot though. Unless a little rock jammed in there or something,
causing sideways force and friction...
Oh well, The Traxxas CVDs 5151R have been added to the MMM backorder

At least they're all metal.