That is quite different from what I expected in several respects, Joe. I'm very glad Rob was on the case. That is an extremely simple transmission, a single speed bevel drive that is clutched by tightening and loosening the belt. It should have lasted forever, with an occasional belt replacement - I'm inclined to guess that there has been a preload error on that pinion bearing, causing it to foul its trousers almost immediately from new. Unfortunately you are going to have to clean everything up very well - there's nothing like swarf attaching itself to the crownwheel to mess everything up. What I don't understand yet is how the mesh is adjusted, and how the pinion bearing preload is controlled. I'm looking forward to more detail on the bits now, as you get to the bottom of it all. Please remember not to try to force things into place by tightening bolts: that may have been what somebody did last time, and caused this debacle.
Ballraces usually have a number on the side of the outer ring, and if you look that number up on the internet, you can find out its availability. Most types are available on ebay at favourable prices.
Oil seals are not as standardised as ballraces, but for lip seals, if you know the inner (shaft) diameter, the outside diameter, and the width, you can search ebay in a flash.
