There comes a time in the life of all manual transmission Mustangs that are sufficiently modified that the factory clutch becomes a serious weak link. That means that many drivers with modified late model Mustangs end up looking for a suitable replacement clutch that will be more appropriate to their needs than the factory part. The modified 2012 Mustang GT we are working on for this story is just such a ride.
When the gang at Cunningham Motorsports bolted a turbo kit to their 2012 Mustang GT, no one expected the factory clutch to make it with the gobs of torque and high horsepower the 5.0 engine ended up producing. The answer to the pending clutch woes for this car was a newSPEC Super Twin clutch and flywheel combination. The team chose a clutch with as close to stock drivability as possible that was able to stand up to the massive power and torque the turbo’d 5.0 now makes. An 80mm turbo was used in the kit, and with 10 psi of boost the GT is putting down 605.2 rwhp and 625.6 rwtq. That is enough horsepower and torque to make the clutch gods weep.
Once a single turbo combination, Cunningham Motorsport's 2012 Mustang made over 625 rwtq at a mere 10psi of boost on an otherwise stock engine.
Before we get into the actual installation of the new clutch, we need to talk about the clutch itself. For this application, with the high horsepower and torque numbers, they chose the SPEC Super Twin clutch kit in SS-Trim. This kit has the capability of handling lots of torque—in the 700-1,500 lb-ft range. Even though the clutch has massive holding power, drivability is still near stock. The clutch has an all-billet construction for longevity and can be rebuilt by SPEC or by a qualified shop.
The materials used in the clutch are top-of-the-line with aircraft-grade aluminum and high-carbon billet steel that is milled to 0.001-inch accuracy for balance and easy actuation. The clutch discs are full-faced carbon graphite discs, and for drivers that want other materials, the kit is available with organic, fiber, and full-metallic options. The kit includes the flywheel and all the hardware needed to attach the system to the engine. This clutch is rated for all driving types including street, drag racing, road racing, time attack, pulling, and rally.
The SPEC Super Twin features an all-billet construction. Some of that billet is aircraft-grade aluminum. Aside from the construction, the Super Twin offers a bolt-in assembly with no setup or shimming necessary
“The Super Twin has set a new standard, offering near-stock drivability, tremendous life expectancy, direct bolt-in installation and maintenance free operation.
David Norton of SPEC Clutch explained, “The problem with clutches that are made to handle the sort of massive torque output modified Mustangs are putting out today is that drivabilty, longevity, and maintenance were issues. The drivabilty was often the worst aspect, with stiff pedals needing lots of leg effort that made street driving a chore. The Spec Super Twin gets around all those issues and sets a new standard by offering virtually stock drivability while being able to withstand up to 1500 ft-lbs of torque.”
Norton continued, “The Super Twin has set a new standard, offering near-stock drivability, tremendous life expectancy, direct bolt-in installation and maintenance free operation. The fact that our clutch is rebuildable as many times as needed provides more value for the driver since the clutch won’t need to be completely replaced when it wears out down the road. Other clutches use single discs and may cost less, but they can’t deliver the kind of holding power and drivability that our clutch provides.”
SPEC Super Twin Clutch Facts:
Near OEM-like drivability
Designed to accommodate over 1500 lb/ft of torque
Bolt-in installation; no shimming required
All aircraft grade billet aluminum construction,
Dampened, full-faced carbon graphite discs.
Organic or full metallic options are available.
With any modification on a Mustang, the first steps are to pull off all the parts that need to move to get to the spot the mechanic needs to work on. The first steps in the case of this turbo’d GT was to get the car up on a lift for easy access, and then the team dropped the stock two-piece driveshaft. Take note that the factory driveshaft is a heavy, bulky item; you will want more than one person to help you here.
After the removal of the driveshaft, the transmission bolts holding the tranny to the engine were removed. Using a jack to support the transmission at the brace near the rear of the transmission, the bolts were removed and the transmission came free of the car. It’s worth noting that when the transmission in a 6-speed Mustang like our project car is removed, you do not need to remove the shifter.
With the driveshaft out and the transmission bellhousing bolts removed, unbolt the crossmember and slide the trans back and down until it's free of the engine.
Understanding the Options
The Super Twin comes in a variety of designs, depending on your power level, including:
PT (puck twin) are puck discs. SST (super street twin) is a fiber disc. ST (super twin) are the carbon graphite discs. ET (extreme twin) has full metallic discs.
We removed the shifter handle, removed the shift bracket under the car, and then pulled the transmission out with the shifter in place. This would be the perfect time to add a short throw shifter to the Mustang, but as you can see in the photos our project car already had a Steeda short-throw shifter in place.
After the transmission was out of the car, we were able to access the factory clutch and get ready for the removal of the stock clutch/flywheel assembly and install our SPEC clutch and flywheel. The removal of the factory clutch was as easy as removing the bolts attaching it to the 5.0’s flywheel. As you can see in the photos, the factory clutch had been abused and was in dire need of replacement.
After getting the factory clutch assembly off the car, we tossed it onto our handy digital scale to see how much it weighed. The factory assembly with flywheel weighed in at 46 pounds, six ounces. After the assembly process for our replacement Spec clutch was complete, we tossed it onto the scale with the flywheel and it weighed in at 38 pounds and 12 ounces, making for a nice weight savings in rotating mass.
After we bolted our new SPEC clutch onto the engine and torqued it to the recommended specs, we reversed the disassembly process and put the transmission, shifter bracket, and drive shaft back into place. It was then time for a test drive to see how well the new clutch holds up to all the power this turbocharged 2012 Mustang GT delivers.
Unbolt and remove the stock clutch, being careful to catch the disc when you loosen the pressure plate. The stock clutch and flywheel combination weighed 46.6 pounds. Even with the additional pieces over the stock clutch, the SPEC clutch and flywheel are significantly lighter, at 38.12 pounds. Less weight here means a quicker accelerating engine.
Before installing the flywheel, inspect the pilot bearing and replace it if it's worn. Hit the flywheel and clutch bolts with a dab of red Loctite to keep 'em tight. Torque the flywheel to the required settings.
You can see here how the clutch discs and slider go together. Also, make sure to thoroughly clean the flywheel and pressure plate friction surfaces with brake cleaner. Getting greasy fingerprints on these areas will reward you with a slipping clutch. In order to get all the clutch disc and input shaft splines to line up, you have to use a dummy shaft (available at any good parts store). Slip it into the pressure plate, line up all the discs, then carefully put it in place on the flywheel, making sure the stub on the dummy shaft goes into the pilot bearing on the crankshaft. Then torque the clutch bolts in place. We set them at 29 ft-lb.
The Driving Characteristics
After the Mustang was off the lift and ready for a drive, Cunningham Motorsports owner (who is also the owner of the car) Ryne Cunningham climbed in and took a test drive. Cunningham said, “The new clutch works great compared to the factory clutch assembly. The twin disc clutch doesn’t chatter, has quick engagement, and is no stiffer than the stock clutch. The car now shifts better than stock and the issues we had with the stock clutch and inconsistent shifts are now gone.”
There you have it, the SPEC Super Twin is a clutch with a tremendous amount of holding power suited to the rough life of drag racing or road racing. While the clutch has the strength to stand up to huge amounts of torque and horsepower, it still retains virtually stock pedal effort and drivability.