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.
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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.
Here’s the before shot of the stock components as they arrive in the 2016 Camaro. Perfectly sanitary, and Bagshaw’s goal is to easily fit a driveline that can handle 1,500+ hp without any cutting or welding on the chassis.
The stock rear differential uses a smaller 8.5-inch ring gear. Notice how the case splits longitudinally. Bagshaw says that when you add horsepower and torque with just a few engine upgrades, this design can cause problems, as the lateral loading from the ring gear pushing on the pinion wants to split the case open. GM has also seen this problem; for the ZL1 Camaro, the company has designed a diff case that opens from the back instead of the side.
On the left is the 9-inch diff housing The Driveshaft Shop uses for fifth-generation (2009–2015) Camaros. The sixth-generation doesn’t vary too much, so Bagshaw will start with the same housing and then find the best way to mount it in the chassis. The diff housing is sized to fit a stronger 9-inch ring and pinion and is designed to handle tons of horsepower. The flanges are cut from billet steel, and the housing itself is formed instead of cut from flat plate to minimize the number of welds needed.
Here’s a shot of the mockup in the car. The housing uses three main attachment points: two on the flange near the yoke and another on the back of the housing. Once everything is square and Bagshaw has confirmed the proper pinion angle, he will tack everything into place and pull the housing out to be fully welded. Before going back into the car, this case will be used to create a jig that will ensure consistency in all future units.
The finished assembly is seen here all powdercoated and ready to go.
Next, Bagshaw worked with the staff at The Driveshaft Shop to put together the full kit, including axles and a lightweight carbon-fiber driveshaft of the correct length. One great feature here is the splines are all rolled into the shafts instead of cut away. By pressing the splines into the steel, it actually compresses the material to make it even stronger than before.
The centersection comes preassembled and can be ordered in a variety of ratios (this one is 3.00:1). The Driveshaft Shop has chosen to use Strange cast-aluminum housings, Wavetrac limited-slip diffs, and Motive Gear AX ring-and-pinion gears for their strength and dependability.
In addition to the rearend, Bagshaw is also installing an upgraded independent rear suspension kit and brakes from Carlyle Racing. So while the axles and rear diff are already out of the car, he also starts on that.
Here’s the Carlyle kit, which includes larger rotors and bespoke Carlyle Racing four-pot brake calipers. That’s a 2-inch wheel spacer at the bottom between the two rotors. There’s a second somewhere, which didn’t seem to make it in the photo.
There are four control arms on each side of the car. Instead of pulling everything at once, Bagshaw cuts way down on the possibility of error by removing one control arm and replacing it with the Carlyle Racing component before moving on to the next.
Before installing the new Carlyle Racing control arm, Bagshaw lays it over the stock unit on a table and adjusts the heim joints until the new arm is the same length as stock. The Camaro will still need a trip to the alignment shop after the install is complete, but this will ensure Bagshaw can take a testdrive with no excessive wear to the tires or driveline components before he can get there.
Compare the Carlyle Racing IRS components to the stock pieces. The top four bars are the stock stamped steel units from GM. Below are two of the Carlyle suspension control arms made from high-strength, thick-wall tubing.
After getting the last of the bars in place, Bagshaw can go back through and tighten all the bolts, including the nuts that lock the length adjusters in place.
The finished suspension setup with the Carlyle Racing drilled and slotted rotors and four-piston calipers.
Finally, Bagshaw is ready to slide the differential in place and bolt it up. The new unit has already been filled with The Driveshaft Shop’s recommend gear oil, Lucas 85W-140 non-synthetic. The unit bolts up using all the stock mounting locations.
Here’s the new centersection bolted up in the cradle.
Bagshaw slides the new axles into position. After sliding the end through the splined hub at the spindle, you may need to use a floor jack to raise the suspension a few inches to create enough room to pop the end of the axle into position on the differential. But once in place, all that’s left is a few bolts to secure it.
That’s the stock two-piece steel driveshaft up top and the replacement carbon-fiber, 3.75-inch shaft below. Besides being significantly lighter, the one-piece design improves efficient transfer of power from the transmission to the rearend. Bagshaw says it is very similar to the carbon shafts The Driveshaft Shop puts on Pro Mod race cars.
Honestly, it takes longer to remove and reinstall all the crossmembers and brackets that get in the way than it does to bolt up the new driveshaft.
This 2016 Camaro SS is finished and ready to laugh at ludicrous levels of horsepower.