When it gets to bitting point that's when the problem starts it sounds and seems like the plates are clashing but only in reverse the car seems to vibrate. Too but only when in Reverse fine in other gears
Could be your gearbox diff, either way you need a new box or a rebuild.
Ive managed to source some info on the net, Its stated below have a read...The problem is that rivets are used to secure the ring gear They've used it since the MK1, and it continued through the 020 boxes, and the 02As even use rivets to secure the ring gears.
They break off. The bits of rivet can wreck (SMS - Self Machining Syndrome) the box. That is one way it fails.
On two of the rivets, the heads are larger, and these large heads are there to secure the cross shaft in the diff, the shaft with the circlip grooves.
Because they use rivets, they don't use circlips. If the head of the rivet breaks off, the cross shaft can float out and SMS the trans. That is another way it fails.
The other way they fail is the lack of a circlip on the cross shaft can allow the shaft to float, and knock on the large rivet heads, already over-worked securing the ring gear, and the heads break off and the first 2 examples result.
The repair is a bolt kit from VW or other sources that replaces the rivets with proper bolts and nuts, and then there are circlips included for the cross shaft. The VW part number for the 020 bolt kit is 171.498.088.A
Both 8V and 16V boxes use the exact same reverse gears and are equally at risk for damage (both also use the same diff, and are equally at risk for diff failure). The damage is caused by not allowing the car to stop before engaging reverse, or by having a faulty clutch which causes the mainshaft to continue spinning, and that will damage reverse. Once chipped, they'll make noise and eventually get worse, until they pop themselves out of gear. The damaged reverse gear is now mating against the other 2 gears, which isn't good for those either, and one is the mainshaft itself.
