part 1 It really does work, (first published October 1987)
The adjustment I am referring to is movement in a horizontal plane of the worm wheel relative to the worm. If you getit really a long way ‘out’ it is possible to get the mos ttooth Jarring grinding from the final drive. do not worry you’ll recognize it. 
The second part of the title refers to the fact that I really do not understand how the adjustment works. so I’ll outline the method the method and leave it to “the brains”. adjustment is effected by moving the position of the nearside differential bearing housing, different positions are obtained by shims between this bearing housing and the differential side plate(the one which has the oil filler in). I demonstrated tomyself recently that as you move the nearside dlfferential bearing housing from a set up where there are no shims betweenit and the side plate to one with a considerable number ofshims the following occurs. First rotation of the whole wormwheel (either with the diff brake drum or both flexible couplings) is easy in one direction and difficult in the other. Then as shims are inserted rotation becomes easyin both directions. Finally with even more shims rotation becomes difficult in one direction. Clearly you aregoing for the easiest movement in BOTH directions. my own opinion is that given the choice forward rotation should be slightly easier.it all sounds very easy, next time I’ll deal with the pitfalls.
Author’s note: The differential assembly offside bearing, although locked to the cageis allowed to “float” within it’s housing, thus the whole left to right position of the cage is governed by the nearside bearing housing, which although locked into position can be adjusted relative to the bronze because the bearing housing itself has shims between it and the side-plate which is bolted to the differential housing. psb