i have a 1990 mk2 16v, i have blown the engine on numerous occasions, but about 8k miles ago i blew a hole in my gearbox, it started bein funny by not goin in 1st or reverse without jammin it hard, then a week or so later i was comin down the m/way and i smell burnin gearbox oil, looked in the rear view and smoke everywhere, took the box off when i got home and i had lots of little puncture holes on the outside of the diff, then there was a 3"x1" hole from the diff to the bell housing. i replaced that box with a second hand one, and this evening i came home down the m/way and all was fine, came off and as i selected second to go round the roundabout it made a serious crunch noise and then some bangin, i looked in the rear view and again i had plumes of smoke, limped home, and as i popped the bonnet i found mainly gearbox oil ans little fragments of gearbox all over the place, why do my boxes keep exploding? is it the way i drive? i use the car like it's meant to be driven, all be it on the track, but i thought thats what they were designed for?? will it stop doin it if i get a recon box or will it just take longer to explode?? i don't wanna get rid of my valver as it's so much fun at high revs but if it's because of the way i drive then i will have to bite the bullet and get something else!
The rivets fail in the 020 diff, and either the head of a rivet is spun around making the holes, or the cross shaft is allowed to slide out (when the rivet head breaks, it holds the shaft in place) and it knocks a hole in the case. We call it SMS or Self Machining Syndrome over here, it is fairly common. The cross shaft is either secured with a set of lock rings on the end, or by 2 special large head rivets, one on each side.... or sometimes both. The rivets can just fail, and the heads pop off, or the cross shaft, on those without lock rings, can be allowed to slide back and forth and beat into the head of the retaining rivet that secures it, and it knocks the head away. No matter how it happens, the end result is the same, the box is shot. VW is aware of the problem, and they offer a bolt kit that replaces the rivets that secure the ring gear. The also provide the lock rings needed to secure the cross shaft. The site in my sig has a Teardown page on it, it shows an 020 being opened, and the diff is riveted, and one has broken off, and mangled the box inside. There is also a Rebuild page, it shows a box being built with a diff that has a bolt kit in it. The page doesn't show the install of the bolt kit, but it shows one bolted up. The rivets need drilled with a 6mm bit then a 12mm bit, and the heads are removed. The rivets are then knocked out of the diff housing with a punch, and the bolts are pressed in, and nuts secure the ring gear. Broke
awesome cheers mate, will look into that, i think i may get a deisel box and see how that handles the power, but i do belive i will loose a bit of top end due to the ratios!
