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Building a 10-Bolt Rearend - Bolt ’N’ GoFrom the August, 2011 issue of Chevy High Performance By Sean Haggai Photography by Sean Haggai
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Proper road-going muscle cars these days have all their bases covered. They can go, turn, and even stop like our late-model favorites. These multipurpose sleds have obtained the appropriate stance through various suspension goodies, and extra grip and decreased stopping distances with wider rubber and an aftermarket brake system. They’re powered through stout mills and their transmissions are built, with the ability to take a direct hit from a tank shell. So what’s left? If you’re paying attention, you’ve realized one vital component is missing from an all-purpose muscle car: a bulletproof rearend to take all the punishment. While your sled may have already come prepped with a posi unit from the factory, ours unfortunately did not. If you recall, our ’72 Nova began its life as a straight-six, which we quickly ditched for a supercharged small-block and a complete suspension and big-brake kit from CPP. We sent it right to work, too, and participated in nearly every autocross event we could enter. We began by properly positioning... We began by properly positioning the Nova’s rear subframe and rearend housing on jackstands. Then, we removed both rear tires and removed the lower QA1 shock bolt with an 11/16-inch wrench and 5/8-inch socket. We further disassembled the components by disconnecting the rear brake lines at the “T” above the differential cover with a 3/8-inch flare wrench. Then, we removed the four large nuts from the U-bolts, which fasten the lower spring perch to the underside of the leaf springs. Note: Check the condition of the brake lines for cracks or abnormal wear. While ’72-75 Novas offered gear ratios from 2.73 to 3.42:1, both with and without posi units, most came with open differential 2.73 or 3.08:1. We got the latter with a set of lazy 3.08:1 gears in our 8.5-inch rear. Leaving stoplights was more of a chore, and exiting turns induced excessive wheelspin from only one tire. With this sort of limitation, remaining competitive was difficult. Besides, what’s the point of all that power with no means of laying it down? Almost every component of the car can become a powerful tool, including the rearend. With power equally distributed at the rear tires, drivers can apply some extra throttle to induce the rear to kick out a bit, point the nose in the intended direction, and go. Plus, for drag-happy drivers, the benefit of having both tires receive traction is that they can produce better launches and quicker times. For us, this was a no-brainer and we researched Moser Engineering’s website to find everything we needed to revive our rearend. This included new 30-spine axles, a 3.73:1 ring-and-pinion, an Eaton posi unit, a performance cover, and even all the bearings, seals, and setup kit. We did all this and still salvaged our factory 10-bolt to house it all. Before the rearend build could begin, we first had to get the factory member out of the Nova. From there, we stripped it down to its most basic form by removing the rear brakes, lines, and sway bar. Then, we sent it to the rearend experts at Manny’s Hardcore Performance (MHP) in Colton, California. All said and done, it took a couple of hours for the build, and we left with a serious piece of equipment for our Nova project.  The large bolt that secures...  The large bolt that secures the upper leaf-spring shackle to the rear subframe was also removed from both sides, using a 7/8- and 13/16-inch wrench. Once this was free, we gently lowered the rear leaves away from the rearend and dropped the housing onto a furniture dolly.  To simplify the build before...  To simplify the build before it went to MHP, we stripped down the 10-bolt to a more basic setup by removing the remaining sway bar and brackets, the entire CPP rear brake assembly, and the lines. A good wash removed years of grime.  At MHP, owner Manny Rodriguez...  At MHP, owner Manny Rodriguez got right to work and removed the factory differential cover with a 9/16-inch socket and drained the old rearend fluid into a pan.  Before we could dig in and...  Before we could dig in and remove the factory ring-and-pinion from the housing, Rodriguez checked the lash on the ring first with a dial indicator. We noted the reading at 0.007-inch lash and were well within the 0.007- to 0.010-inch recommended specifications. This meant our factory 10-bolt was still in great shape, and we could start the disassembly.  We first removed the main...  We first removed the main cap (passenger side), which allowed us access to the small set bolt that keeps the pin from dropping out of the spider gears. We used a 1/2-inch box wrench to remove the bolt along with the pin. With the pin removed, we gently pressed on the axle, removed the C-clip from the axle notch, and pulled out the axle. Note: Only remove one cap at a time; otherwise the entire assembly may fall out of the housing.  From there, we repeated the...  From there, we repeated the process on the other side by removing the driver-side main cap, C-clip, and then the axle. We then carefully removed the factory carrier assembly from the housing. Make sure the main caps are not mixed.  We used a large socket to...  We used a large socket to remove the pinion nut and used a brass punch and hammer to remove the pinion.  Don’t have an axle seal puller?...  Don’t have an axle seal puller? Rodriguez showed us a quick tech tip by utilizing the end of the axles to remove the seals. Once the seals are removed, we used a bearing puller to extract the old axle bearings, which we ditched since Moser supplies all-new ones. Moser offers forged steel street axles for both the 10- and 12-bolt rearends. They are made from the same alloy as the race axles and are approximately 25-30 percent stronger than OEM (depending on spline count). These axles are nontapered, with hardened bearing seats and machined C-clip grooves to fit OEM applications. Plus, they’re available in any length up to 37 inches and can be shortened or resplined at a later time, should you choose to narrow your existing rearend. For our application, we ordered Moser’s axles in the stock 29 1/2-inch length in a 30-spline configuration.
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