Reading some of the previous posts it seems that the permanent solution to the problem is to get the bevel gears lapped, which is what the company should have done in the first place. It's MMC or Quaife saving pennies, I suspect MMC instructed Quaife to build it to a price.
I have copied and pasted from Ricardo's post.
WHAT IS GEAR LAPPING?
Gear lapping servicesGear lapping is the process of imparting a very fine finish and high degree of accuracy to gear teeth, by using a lapping tool and applying a fine-grained abrasive between a work material and a closely fitting surface, called a lapping plate. By running mating pairs together in a gear lapping machine and feeding a liquid abrasive compound under pressure into the gear pair, small amounts of metal are removed as the gears rotate, thus refining the tooth surface and achieving the desired contact pattern.
Lapping typically improves the wear properties of gear teeth, and corrects the minute errors in involute profile, helix angle, tooth spacing and concentricity created in the forming, cutting or in the heat treatment of the gears. Therefore, gear lapping is most often applied to sets of hardened gears that must run silently in service. It is important to bear in mind that gear lapping is a mating process; two gears that have been matched by lapping should be operated as a set, and also replaced as a set, rather than singly.
