The 36-spline spool for 9, 9 1/2 & 10-inch gear applications was designed to address several problems encountered with other manufacturers' spools. First and foremost was the issue of breakage of the bearing journals due to inadequate material thickness on other 4-inch bearing type spools. Years of practical experience dictated that the 2.562 in. 40-spline axles were more than strong enough so it was decided to size it down four splines to 2.375" 36-spline. The second was the required modification of an already very expensive carrier bearing. This 36-spline spool uses the Timken L713049 just as it comes out of the box with no modifications. Third, some spools center the axle in the center of the spool, this is usually the thinnest section in a spool and most prone to failure. In this spool, the axles are centered at the ring gear mounting plane, the strongest part of the spool.