I have found that the mcmaster thruster and races are of equal quality to the stock, or they may even be the exact same parts. It is also important that your mainshaft end float be checked to not to be too excessive. I have a box on my bench right now where a self appointed "mechanic" had installed a bogus end shim that was at least .030 inch too thin and a whole lot of slamming back and forth had occurred. The bevel gears are very tough and I could see no problems with them, but the 5th gear shifter fork had extreme wear on the pin that rides in the drum. The thing must have had to be forced into gear, or maybe even held there. Guzzi has about 4 thicknesses of end shims listed. For me, .005 to .012 inch mainshaft end float seems to work. Getting the drum and this shaft properly shimmed will make for a way better shifting and trouble free box.