Ok gang, if like me your washers are missing or seen better days and you don't want to spend over £200 for some NOS old rubber, here is a simple solution. I kept getting clonks when on power and the rear wheels going over very lumpy roads. Particularly bad on the left side. Lo and behold, no serrated washer in sight on the left and just one top one on the right. Clearly the moustache bar is connecting metal on metal when loaded up. What you see at the top of the pic is my first attempt with butchering an old Audi Q5 ARB bush - that made it better but didn't work well enough. I took a poly compression bar bush that I am no longer using and it appears to be a near perfect size. (Using poly on front of compression bar and rubber at the rear). http://www.thezstore.com/page/TZS/PROD/classic20m01b/23-4138 I cut it roughly into quarters with a hack saw - measuring my one remaining bush, it's about 10mm depth. I went closer to 8mm to allow some room for the moustache bar to move freely. I couldn't be bothered with taking the bar / diff off to fit so I added a cut to be able to slide it on around the bolt - Pacman style. After some sweaty effort and mild language it went on. Being poly it was hard to open up the mouth to slot it in. However, on the upside once past the bolt it just "clicked" into place and it's never going to come out without dismantling. Ideally I would have used a rubber bush but uncompressed they are smaller; the poly bush uncompressed is practically spot on to within a couple of millimetres. I'll do a better photo of the other side when I next Jack the rear up. Over 50 clunk free miles (including some serious "old boy-racer" antics) later and I feel happy enough with the result to write it up. Not a clunk except from the diff mount insulator when coming off the power during old-boy-racer antics; which will have to wait until I transplant the 3.9 diff.