i believe the rivet likes to fire around the gearbox making a mess of things or get squashed somewhere and pop a hole the the casting which your oil leaps through- if your a really unlucky person itll go on your tyres and brakes but either way its all over for the gearbox so its prevention rather than cure.... you shouldnt lose all drive till all the rivets are out, although there are other ways to bugger a gearbox!
got my next one reserved in a mates shed so itll be bolted and doweled before its fitted, also going to turn up a copy of the peloquin preload rings as i dont have 600quid for an lsd and if i did id spend it on another mk2 an e30 beemer a night out and some really nice trainers so there!
anybody know if you can get gearbox rebuild kits, bushes/bearings seals etc- may aswell do it while its apart i spose