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Building a 10-Bolt Rearend - Bolt ’N’ Go

Sean Haggai Jun 22, 2011
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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.

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.

Forged C-Clip Sticks


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.

Detroit TrueTrac


The Detroit TrueTrac was the first helical gear (no clutches) differential ever introduced into the aftermarket as an Eaton brand. In short, the patented design of the parallel axis planetary helical gears provides a quiet, automatic splitting of torque. It performs like an open differential under normal driving conditions and automatically transfers torque to the wheel with better traction. This limited-slip system responds instantly to torque feedback, anytime, at any speed.

Geared For Go


Moser’s gears are available for nearly any application and are CAD, CNC machined, and computer-control heat-treated to ensure the highest-quality product. Moser even offers a ring gear lightening program (add $100 to any set of gears) for serious racers to save precious rotation weight. The process involves machining a smooth radius on the outside of the gear and can save anywhere from 0.5 to 2.5 pounds. In our case, we ordered a set of Moser’s street/strip gears with a 3.73:1 setup.

The Grab Bag





Moser 3.73 ring-and-pinion 10B85373M $190
Differential cover 7107 160
30-spline axles (291/2 length) A103002 245 (pair)
Eaton TrueTrac 5TT481 550
Setup kit/axle bearings, seals R10MB/9563 100/30 (pair)
Royal Purple 75W90 rearend fluid 01300 18

Road Report


Getting the rearend back in the Nova was a snap. We made sure to fill the rearend with 3 quarts of Synthetic Royal Purple 75W90 gear oil (for limited-slip gears) and put some miles on the gears before any competition. While at this year’s Goodguys Del Mar event, we noticed the Nova’s characteristics and personality have completely changed since our install of the Moser components; it’s like driving a new car. Wasted power that used to be directed to one spinning tire is now equally split between two. This translates into faster times through the cones and makes more use of the available power. We can even have a little fun in the turns now by sliding out the back end with some extra throttle. Plus, burnouts have become a lot more interesting. CHP


Royal Purple
Porter, TX 77365
Moser Engineering
Portland, IN 47371
Manny's Hardcore Performance



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