Had a strange metal on metal grinding during shakedown run on my coupe. Safety retainer was not very safe ! How the hell the PO fucked up this install is beyond my comprehension !!!!
I ran them on my avatar with no problems, decided they aren't really necessary and didn't use them on my A V8. I've sheared axle keys but never broke an axle with my flatheads or 4 bangers.
I had to do a lot of grinding to make those things fit on the back of my '40; but I've had bad experiences with tapered hub axles so will run them until I upgrade to modern axles.