Gordon,

The locking tabs don't fail in terms of breakage. But if the forces are high enough, they can release the fastener. I doubt this could happen to the oil pump since it's not under a lot of stress. But I have seen ring gear bolts back out

http://forums.pelicanparts.com/uploa...1555942397.jpg
http://forums.pelicanparts.com/uploa...1555942409.jpg


The above diff was from a '79 915 trans run very low on oil. Apparently the heat & stress on the ring gear caused the bolts to back their way out. Looks like the flats of the bolts pushed past the bent ends of the locking plates.

I recently took a ring gear off of a LSD and the tabs are fairly sturdy metal. It takes quite a bit of force with a hammer and punch to maul the locking plates off the bolt heads.