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How to Put a 9-Inch Rear in a 2016 Camaro

HOT ROD logo HOT ROD 8/5/2016 Jeff Huneycutt

It's a fact that we are living in a golden age of horsepower. Just a decade ago, a 500hp engine was a really big deal—and pretty expensive. But now all the Big Three have special vehicles eclipsing that number. All you have to do is tick the correct box on the order sheet.

As impressive as that is, it's nothing compared to what smart engine builders are doing. Guys all over the country are throwing a supercharger or twin hairdryers on a well-built small-block and coming up space-shuttle levels of thrust. It is easier than ever to come up with triple-digit horsepower numbers on engines running pump gas. Even occasional readers of Car Craft know exactly what we're talking about.

The problem is that you simply can't plug in a thousand or more horsepower into practically any street car without blowing stuff up real quick. So it's mandatory to upgrade the rest of the driveline to be able to handle the torque of your high-horsepower engine.

The Driveshaft Shop in Salisbury, North Carolina, specializes in designing and manufacturing extremely high-performance drivelines for modern cars utilizing independent rear suspensions. Their stuff is in drag-race cars, drifters, land-speed racers, and everything in between. You can find their designs in Vaughn Gittin Jr.'s 900hp drift Mustang and Mark Carlyle's Corvette—the current record holder for a independent rear drag car with a 6.58-second pass at 220 mph.

We recently had the opportunity to spend a few days documenting the process as The Driveshaft Shop worked with fabricator Scott Bagshaw of Bagshaw's Hot Rod Fabrication to develop a new 9-inch independent rear for the 2016 Chevy Camaro. As far as we can tell, it is the first 9-inch, bolt-in rear for the sixth-generation Camaro. Like the earlier Camaros, the 2016 model uses an 8.5-inch ring gear, but while the differential housing is similar, it does use a different mounting point. In stock trim, GM's rearend design is perfectly acceptable, but we've heard that once you start exceeding 600 hp—pretty easy to do with modern LS technology—owners have started seeing problems.

To fix that, Bagshaw pulled together some of the best stuff from The Drivehsaft Shop's extensive parts bins and fabricated the rest to develop a true bolt-in kit that can handle 1,500 or more horsepower. Surprisingly, the kit—which will include a carbon-fiber driveshaft, a steel differential housing, a 9-inch ring-and-pinion set, Wavetrack limited-slip differential, and axles—will bolt up with no cutting or welding required. Our first question: If it bolts right up, how can it be so much stronger?

"A lot of the strength comes from the material choices," explains Frank Rehak, owner of The Driveshaft Shop. "Take the axles, for example. From the factory, they are going to use a material that's induction-hardened so it's going to be hard on the outside and soft on the inside. It's quite strong, but like a clothes hanger being bent repeatedly, it is eventually going to fatigue and break. It isn't a question of whether it is strong enough when the car is new, but how many fatigue cycles it can withstand? And the more power you put to the rear tires, the harder it is on those axles. Our axles aren't stronger because they are a lot bigger, they are stronger because we use a 300M steel. It's the same stuff that's used on helicopter rotor drives and commercial aircraft landing gear. Fatigue cycles really aren't an issue with this material, even if you have well over a thousand horsepower. You can twist it and it just keeps coming right back."

The rest of the axle is similarly well-built. Rehak says the CV joint cages are cut from billet chromoly steel, while the races are the same 300M material as the axleshafts. They also use a stronger 30-spline size feeding into the limited-slip diff, and the splines both at the diff and the hubs aren't cut out of the shafts but rolled in. It's the same process as manufacturing a high-strength head bolt, and it compresses the material to actually make it stronger than before.

Rehak also gave us some interesting background on why carbon-fiber drivehsafts are becoming so popular among the really fast street cars. While the lighter carbon fiber is better than either steel or aluminum when it comes to reducing the moment of inertia, that's not really the biggest advantage.

"Being lightweight is nice, and it also makes balancing the driveshafts easier without adding significant counterweight, but the real advantage of a carbon-fiber driveshaft is its ability to absorb torsional shock loads and not release them like a spring," Rehak explains.

"When you put a shock load into a steel driveshaft," he continues, "it can twist 5 to 7 degrees. The driveshaft twists up torsionally and then releases that energy just like a spring, which can upset the car. Aluminum kind of does the same thing. It can twist up to 20 degrees, but it does not unload as quickly. Carbon, meanwhile, twists up to 30 degrees. But unlike steel or aluminum, it won't spring back right away. It will hold that twist until the torque is taken off the driveline. In a drag-race application, it can really help the 60-foot times tremendously. In a typical street/strip car, you can see anywhere between a drop of 0.1 to 0.3 of a second in the 60-foot times just by switching from steel to carbon fiber."

The car Bagshaw is working on is a brand-new 2016 Camaro Super Sport that the owner gave permission to use as a test mule. In the future, there are plans for big horsepower upgrades to the 455hp LT1, so along with the new kit from The Driveshaft Shop, Bagshaw is also installing an independent rear suspension and brake upgrade kit from Carlyle Racing. It, too, is a bolt-in—of course.

Axles, a larger 9-inch gear, and a carbon driveshaft may not be nearly as sexy as a big blower up front, but this does make an excellent foundation so the car will be able to handle dump-truck loads of additional torque. You will also notice in the photos that Bagshaw did all the design and development with the Camaro sitting on jackstands instead of raising the car up on a lift. The point is to show that this install can easily be done with basic handtools in your driveway over a weekend.

The Driveshaft Shop partners with expert fabricator Scott Bagshaw whenever it puts together a new driveline kit capable of handling thousands of horsepower worth of punishment. We spent a few days at Bagshaw's Hot Rod Fabrication watching Bagshaw put (as far as we can tell) the world's first 9-inch rearend in a 2016 Camaro.

The Driveshaft Shop partners with expert fabricator Scott Bagshaw whenever it puts together a new driveline kit capable of handling thousands of horsepower worth of punishment. We spent a few days at Bagshaw's Hot Rod Fabrication watching Bagshaw put (as far as we can tell) the world's first 9-inch rearend in a 2016 Camaro.
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