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Chevy Chevelle Rear Axle Swap - The Great Rear Axle Comparo

How Much Horsepower Does It Take To Spin A 12-Bolt, A Ford 9-Inch, Or The Big Strange S60? We Find Out.

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We've all heard that the Ford 9-inch is the strongest rearend you can buy. According to the Ford guys at least, it's also the best overall decision for strength and durability. If pressed, they'll also accept that the 9-inch might eat a little more horsepower than the other-style rearends. Numbers are also tossed about like resolutions on New Year's Eve, but no one seems to know exactly. We've also heard that the Dana 60 is a killer piece but that it's monster heavy and overkill for anything short of a blown Hemi on steroids. What you also notice is that opinions on strength and efficiency tend to follow party lines. In other words, the Ford guys will vote for the 9-inch, the Chrysler guys will wave the Dana 60 flag, while the GM guys all line up behind the 12-bolt. No surprises there.

We decided to cut through the brand-loyalty blindfold to take a clinical look at the 12-bolt, the Ford 9-inch, and the Dana 60 rear axles. We obtained a 3.50:1-gear version of each of these three rear axle assemblies that would bolt into an early Chevelle to see which one eats the least power and also investigate how strong each assembly is, relative to the others. We enlisted the help of Currie Enterprises, Moser Engineering, and Strange Engineering to supply both parts and expertise with this evaluation. Then we chassis dyno-tested all three at Westech on a SuperFlow SF-790 using our small-block Chevelle to see which one could put the most power to the ground. We chose a Chevelle mainly because it was accessible and because the 383ci small-block made decent power at the crank. The results were certainly worth the effort.

GM 12-Bolt
We started with a stock, early Chevelle 12-bolt housing that had been modified by Sutton Engineering with Moser large Ford bearing housing ends that allow the use of either stock drum brakes or a bolt-on disc-brake package. Because the original 12-bolt housings are now more than four decades old and hoarded by collectors, Moser offers brand-new bolt-in housings along with axles for a reasonable price. The larger Ford bearings are much stronger and use a four-bolt axle retainer plate, like a Ford 9-inch. This eliminates the stock C-clips and uses an aftermarket Moser 30-spline axle. We could have opted for a 33-spline axle, but we felt we didn't need that kind of strength for this test.

We also spec'd a set of Moser 3.55:1 street gears, a Detroit TrueTrac limited slip, and a 1310-series U-joint pinion yoke. To add a little more strength, we also included a Moser aluminum rear cover that uses Allen preload bolts to support the main caps under load. Tim Moore installed the ring-and-pinion for us. While we chose Moser as our source for 12-bolt parts, Currie and Strange also offer complete 12-bolt rearend assemblies as well as individual components.

Moser 12-bolt housing, A-body Call Moser Moser Engineering $919.00
Moser 12-bolt housing ends 7900 Moser Engineering 80.00
Moser 12-bolt retainer plates 9900 Moser Engineering 15.00
Moser 12-bolt 30-spline axles Call Moser Moser Engineering 315.00 pair
Moser 12-bolt 3.55 gears 12B355R Moser Engineering 210.00
Moser 12-bolt pinion yoke, 1310 PY110 Moser Engineering 90.00
Detroit TrueTrac, 30-spline 5TT555 Moser Engineering 465.00
Moser aluminum cover 7110 Moser Engineering 160.00
Moser setup kit R12B Moser Engineering 100.00
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