Clutch Decision
Lethal Performance upgrades its blown GT350 with a McLeod Racing clutch
By Steve Turner
Combine the high-winding Voodoo 5.2-liter engine with a whiff on nitrous and it’s no surprise that you might find a fusible link in the driveline. In the case of Lethal Performance’s Shelby GT350 project, that link was the factory clutch.
Now a clutch is an easily replaced wear item, but in the case of the latest Shelby Mustang, there were no aftermarket alternatives with which to upgrade the stock clutch. Lethal soldiered on with its modifications, including a Whipple supercharger, but the company new that even a fresh stock clutch wouldn’t survive another round of track testing.
“We upgraded to the McLeod Racing setup as we smoked the stock assembly our first trip to the track when we ran 10s on nitrous,” Jared Rosen of Lethal Performance explained. “We always run McLeod Racing clutches in our cars. So when the stock assembly went bye-bye we made the call to McLeod to start working on a replacement. We chose the RXT HD setup as it best fits the current power level the car is making as well as what type of driving we do with the car on the drag strip and road course.”
To remedy that problem, Team Lethal partnered with McLeod to develop an RXT 1200 twin-disc clutch to harness all that supercharged Voodoo power and channel it through the factory Tremec 3160 six-speed manual transmission.
“So the GT350 clutch from McLeod needed to be designed from scratch. Another thing that was taken into account is that harmonics on the flat-plane-crank GT350 have been questioned,” Jared said. “So the judgment call was made to design the McLeod clutch to match the weight of the factory setup so not to affect any possible harmonic issues.”
McLeod already had one of these clutches in mind to back up the Voodoo engine.
“The RXT 1200 was designed with cars like the GT350 in mind. The type of car that has the potential to make great horsepower yet the clutch can quickly become the weak link,” Bob Scheid, Director of Business Development at McLeod Racing, explained. “The average GT350 driver also tends to use their cars on the street and at the track. The RXT 1200 had to be good for both driving experiences. Lastly, GT350 customers want the best performance at a price that is affordable. The RXT 1200 had to be the best quality twin-disc yet we had to make it so folks could afford to buy it.”
That’s where Lethal was able to help expedite the development process.
“Since the GT350 is so new and no one had actually seen the stock clutch fail or seen one in person it was vital for us to ship the stock assembly to McLeod for them to take a look at,” Jared added. “Come to find out that the GT350 stock clutch is completely different then the 2011-2017 Mustang GT clutch. The 2011-2017 GT clutch setup places the pilot bearing in the crankshaft where the GT350 places it in the flywheel.”
Of course, the Voodoo engine’s flat-plane crank is now legendary, but along with that design comes some unique challenges to minimize the harmonics associated with that crankshaft. That meant McLeod had to take special car to balance its more robust RXT twin-disc just like the factory unit.
“The biggest challenge in designing this clutch was never sacrificing quality while still keeping the price very affordable. Our design team did such an awesome job staying focused on our customer’s needs,” Bob said. “With over 45 years of experience, McLeod is able to do things other clutch companies just can’t. McLeod relies on the experience we have on the track to help us build the best clutches for both street and track use.”
Fortunately that expertise means you can install a more robust clutch without sacrificing the driveability of your GT350.
“The RST/RXT lines have become so popular and so sought after because they do have distinct advantages over other clutches on the market. The pedal effort is excellent,” Bob added. “No heavy pedal means a clutch that is more enjoyable to drive. We also used the very best friction materials to keep clutch from chattering, extend clutch life and give excellent holding power at the track.”
Better yet, installing this clutch is a true remove and replace operation, which we witnessed in person at Power by the Hour in Boynton Beach, Florida.
“The RXT 1200 is also an easy install. Simply unbolt the six bolts that held up the OE clutch and bolt up the RXT 1200 in its place,” Bob said. “Since The RXT 1200 for the GT350 has its own drive plate there isn’t even a need to resurface the flywheel. Performance, affordability and ease of installation were all major factors we would not compromise on.”
Follow along as PBH’s Donnie Renfrow preps the Lethal GT350 for its next adventure…
To harness the 800-plus rear-wheel horsepower produced by its Whipple-supercharged Shelby GT350, Lethal Performance turned to McLeod Racing for one of its RXT 1200 twin-disc clutches to replace the wounded factory clutch (right).
Donnie gets started by removing the exhaust, which also paved the way for a complete Kooks Exhaust upgrade.
With the transmission properly supported, Donnie unbolted the BMR Suspension driveshaft safety loop which also frees the factory transmission crossmember.
Donnie unbolts The Driveshaft Shop carbon fiber shaft to clear the way for removing the transmission.
Donnie removes the starter before unbolting the transmission bellhousing. Here you can see the extra brace that retains the starter on the Voodoo engine.
Using a transmission jack, Donnie wiggles the input shaft out, then slowy lowers the Tremec 3160 out of the way.
Knowing the factory clutch had been slipping for some time, we expected it to be covered in its own dust. It actually didn’t look too bad.
Here’s a look inside the compact, sprag-driven factory clutch.
As you might guess from its name, the McLeod RXT 1200 is designed to corral up to 1,200 horsepower. It does so by still keeping the pedal effort light thanks to its twin-disc design.
Donnie removes the RXT 1200 from its flywheel, which is the only setup necessary.
Next he bolts the flywheel onto the crankshaft using the stock hardware and torques the bolts to factory spec.
Then Donnie installs the RXT 1200 and torques it to the flywheel. Now the car is ready for reassembly.
He then reverses the process, bolting up the bellhousing, crossmember/safety loop, starter and driveshaft. Now the Lethal GT350 is ready to put down some serious power on the drag strip, road course and street.
