The main complaint heard from 489 critics is a partly deserved reputation for durability issues stemming from the 489’s collapsible pinion-support collar (right). For mass-production efficiency, the collar is designed to crush a prescribed amount when the pinion nut is torqued to 300 lb-ft. The controlled deformation delivers the specified pinion preload. The problem is that shock load generated by repeated dragstrip launches with sticky tires can further compress the collar, especially with a manual transmission and a heavy car. This changes the preload and leads to breakage. Substituting the solid non-collapsible collar from Ratech (RatechMFG.com) cures the problem. Assembly reverts to the process of juggling select-fit shims (as employed on the 741 and 742 diffs), but the end result is worth it. Our ring gear is etched with setup markings that read “CD 2.769,” indicating that the compression distance is 2.769 inches. The Ratech collar is PN 4103 and sells for a mere $33.