The crown wheels and pinions are vastly improved to the original cars, I still try to shim the diffs correctly but there is a greater tolerance now, I think I might only have one shim in each diff. I also used to need to regrease the diffs after every meeting to help prevent wear but I only do it after every 4 meetings or so now.
Apart from direct from xtreme you can now get spares from
http://theraceplace.co.uk/osCommerce...hp?cPath=34_68 but I haven't actually ordered anything from them yet so I can't say anything about their service.