Maximum-Effort Fourth-Gen10-Bolt

The side-bearing races and shims are removed from the installation kit, and a micrometer is used to measure the supplied shims. On average, the standard 7.625-inch differential has between 0.470 and 0.480 of shims in total. Each side has 0.235-0.240 worth of shims. After completing the measurements, Jason came up with 0.232 on the passenger side (0.205 + 0.010 + 0.010 + 0.007) and 0.244 on the driver side (0.205 + 0.032 + 0.007). The 0.476 total is right in the middle of the average.

After the side-bearings' race saddles are wiped down, the races are installed, and the differential and shims are slipped into position. At this point, Jason realized the shim thickness on the passenger side was too much because the differential and shims wouldn't fit in without significant effort.

The differential is removed, and the shims are adjusted to 0.242 on the driver side and 0.230 on the passenger side (a total of 0.472). Next, the differential and shims are reinstalled, and the shims are tapped in with the proper amount of effort using a side-shim installation tool and a hammer.

After cleaning the stock bearing caps and bolts, a light coating of gear oil is placed on the inside of the bearing caps. A torque wrench and 51/48-inch socket are used to torque the main bearing caps to 55 ft-lbs. To ensure that the differential moves freely and is properly seated in the races, it is rotated back and forth.

Before setting up the dial-indicator to measure backlash, the gasket-mating surface has to be clean. A wire-wheel attachment on an air-powered die grinder is used to knock off the powdercoating allowing the dial indicator's magnet to stick properly. Once complete, the surface is cleaned with a grease and wax remover, and a blow-nozzle attachment is used to disperse any residual powder that settled into the housing.

With the housekeeping out of the way, a dial indicator is attached to the gasket surface and set up to make contact with the near heel-end of the ring-gear tooth. After zeroing the dial indicator, a backlash measurement is taken on 3-4 locations on the gear. The factory specification is 0.005-0.009 of backlash. Jason measured a 0.003, 0.004, and 0.005, for an average of 0.004. As long as the measurements don't exceed 0.002 between the high and low numbers, it indicates the case isn't distorted and the factory torque procedures were adhered to properly. Unfortunately, 0.004 isn't between 0.005 and 0.009, so the differential has to be removed and adjusted.

Since the ring gear needed to be moved away from the pinion by a minimum of 0.001, the shims were adjusted to 0.238 on the left side and 0.234 on the right side, and the dial indicator was used to take new measurements. This time the measurements came in at 0.0075, 0.007, and 0.007, or an average of 0.0072, which is right smack in the middle of the specification. According to Bailey, "It isn't uncommon to pull the differential 3-4 times in order to get the backlash correct. Since the proper backlash is a crucial factor in determining whether a ring gear will operate quietly and perform to expectations, it has to be right on."

Before claiming victory, the supplied, yellow ring-gear marking compound is brushed on one half of the ring gear and rotated back and forth so that a pattern can be discerned.

The object of marking the ring gear with compound is to make sure that the contact pattern is in the center of the ring-gear tooth. As you can see in the photo, the pattern is perfectly centered, indicating the pinion depth was measured and was accurate. However, checking only the drive side of the ring gear teeth isn't sufficient.

The coast-side pattern is closely examined to make sure that it's also in the center. If either side has a low or high contact pattern, the pinion shim thickness has to be increased or decreased accordingly. A low pattern indicates the pinion is too close to the ring gear, and the shim thickness has to be reduced. A high pattern indicates that the pinion is too far away from the ring, so the shim thickness has to be increased. It may only take 0.002 or 0.003 of shim adjustment to correct the gear-contact tooth pattern, but failure to have an even pattern in the center of the gear often results in either noisy operation or the ring or pinion shearing a tooth. After verifying the pattern, a grease and wax remover is used to clean the yellow marking compound off of the gears.

Now that the differential is completely assembled and set up per factory specifications, the axle ends are cleaned and a replacement bearing is inserted. A J23765 axle bearing installer is used in combination with a hammer to set the bearing into position.

Once complete, a new axle seal is driven into position with a seal driver and hammer. RTV isn't necessary on the axle seal as it already has a sealant that is effective in keeping the oil in the axle tube for decades!