Strengthening The Rearend From An LS1 Firebird Formula - Maximum-Effort Fourth-Gen10-Bolt

With the differential on a table, we prepared to remove the ring gear. This is when you determine what GM rearend you have. There were 10-ring gear bolts, making this a 10-bolt. On some GM heavy-duty applications, such as 3/4-ton trucks, there are 14 differential cover bolts where the ring gear has 12 bolts. This constitutes a 12-bolt rearend. We removed the reverse-thread bolts that hold the ring gear to the differential with a 3/4-inch socket. Once all 10 bolts were removed, the ring gear was separated from the differential by inserting a punch in a bolt-hole and tapping it with a hammer. After turning the differential over, a brass punch was used to carefully tap the ABS reluctor wheel off the differential.

Once complete, the axle housing and bearing caps with bolts were transported to Peyton Automotive Performance to be serviced. Due to the relative light weight of the housing, abuse on the street or drag strip could have caused distortion in the axle tubes or other issues with housing straightness. Since the axle tubes are only press-fit into the 10-bolt, extra rigidity was achieved by welding the axle tubes to the housing. After welding the axle tubes, the housing (with caps bolted on) was set up in a jig and carefully measured for straightness. After it was determined where the housing assembly needed attention, a hydraulic press was used to bend the unit until the housing and axle tubes were squared up. It should be noted that some degree of housing distortion in the assembly is common and easily corrected. In this case, the distortion was minor.

A complete Yukon rebuild kit was supplied by Randy's Ring & Pinion. The kit (PN YK GM7.5-B) contains all of the parts necessary to rebuild the rearend. Yukons axle bearings (PN AK1563) and seals (PN 8660S) round out the package and an excellent 19-page installation manual is included as well. All bearings are top quality Timken units while the seals are from National.

Rather than use a wire brush for cleaning and paint to cover the bare metal, the housing was sent to Enduro Powder Coating in Garland, Texas. After sandblasting the housing down to bare metal to remove all of the surface rust, it was baked in a powdercoat oven in order to draw out any potential contaminants in the housing, such as oil and grease. Following a thorough wipe down, a semi-gloss black powdercoating was applied; then cured in the oven. Once returned to the shop, hot water and a soapy degreaser were used to clean any residue out of the housing and axle tubes. The pinion race bores were then cleaned with a grease and wax remover ..

... and thoroughly inspected. Once it was verified that the sealing surfaces were blemish free, the outer pinion race was installed using a hammer and OTC race driver. Then the housing was turned over, and the inner bearing race was installed.

Next, the pinion depth was checked with a comprehensive Kent Moore J34925 tool (J-tool) set. Before installing the tool, the bearing-cap seating surfaces were inspected. In this case, some errant mediablasting required polishing the right-side main bearing surface with an emery cloth before both surfaces were wiped with a grease and wax remover. The races and pinion bearings were lubricated with gear oil and mounted onto the J-tool. After turning the housing over, the pinion nut was installed and torqued to 20 inch-pounds to properly seat the inner and outer bearings.

The J-tool gauge block was installed at the pinion bearing, and remaining tool components followed, and are held in by the bearing-cap bolts which were torqued to 55 ft-lbs. The tool was manually rotated back and forth to make sure it moved freely and was properly seated.

A dial indicator was mounted against the J-tool's plunger. The J-tool was rotated slowly back and forth, and the dial indicator was reset to zero. Next, the J-tool was rotated until the plunger moved off of the gauge block. This resulted in a reading of 0.033, calling for a 0.033 shim.

The J-tool was removed, the housing was rotated, and the outer pinion bearing was installed. A light coat of silicone RTV was applied to the edge of the new pinion seal and a J-23911 pinion-seal installer was used to drive the new seal into the housing. Although the service manual doesn't call for RTV on the seal, it's highly recommended to ensure a leak-free seal for years to come. All too often, brand new F-bodies had leaking pinion seals before their owners even took possession!

A micrometer was used to find a supplied shim or combination of them that measures 0.033; then came the replacement set of Yukon 3.42 gears. After cleaning and lubricating the pinion seating surface on the new pinion gear, the shim was installed and the bearing was pressed onto the pinion using a J-8609 tool.

Next, the crush sleeve was slid over the pinion, and the assembly was installed in the housing. The pinion yoke, washer, and pinion nut were next. Finally, using a 1-1/4-inch socket on an impact gun, the pinion nut was tightened in small increments to reduce the play and preload the bearing.

After beginning to feel preload on the bearing, an inch-pound torque wrench was used to measure the preload both clockwise and counter-clockwise, shooting for 20-25 inch-pounds. After initially determining a preload of 16 inch-pounds, the pinion nut was tightened again and rechecked. This time the reading came in at 25 inch-pounds, which is right in the middle of the 15-35 inch-pound specification for new pinion-bearing preload. If it goes beyond 35 inch-pounds, the pinion must be removed and a new crush sleeve installed.