Just about anyone who owns a muscle car can admit they usually have only two things on their mind: power… and how to get more power. With the goal of maximum performance and minimal e.t.’s in your sights, you most certainly need to think about upgrading your clutch. That is exactly what we did on our ’03 Mustang Cobra – we built a new engine that was slated to make over 850 hp – but we knew that the clutch installed in it would be crying for mercy. McLeod Racing came to the rescue with one of their trick 1,000 HP capable RXT’s. Let’s review the new clutch and overview our installation:
McLeod Racing has designed and built clutches for thousands of different stock and high performance applications since Red Roberts and his brother opened McLeod Racing in January of 1971. Even though the performance demand has changed vastly since they opened their doors, they had the same business objective in 1971 that they do now: to build top of the line clutches that can withstand high amounts of power.
In fact, we recently took a tour of McLeod Racing, you can check out the video below, or skip it for our tech article!:
The Cobra: An Angry 850 HP
Our 2003 Mustang Cobra originally hit the track with a supercharged 4.6-liter modular engine that made about 590 rwhp and ran mid 10-second e.t.’s. After about 40 runs down the track and 11,000 miles on the road, the stock 4.6L Cobra engine expired which resulted in the need for a total rebuild. We sent the motor up to Ford Performance Solutions where Troy Bowen and his crew built a bullet that was no joke.
Looking for 850 horsepower, we slid in new JE 9.2:1 compression forged pistons, four COMP cams modular 4-valve camshafts, a complete Aeromotive fuel system, CNC ported the heads, and added a larger Whipple 3.3 liter supercharger. It all added up to a combination that will make 700 streetable rear wheel horsepower and will do it’s best to rip the clutch straight out of the bellhousing.
We needed help, and we needed it bad. McLeod Racing, are you there?
Designing The RXT Clutch
Designing a clutch starts with an idea and concept. For the RXT, that idea was to build a clutch that could stand up to 1,000 horsepower with a very reasonable pedal pressure. That’s tough. “When cars reach a certain amount of hp, they need more holding power,” Fred Taylor of McLeod Racing told us. “The tough part is making a clutch that you can live with.”
McLeod Racing told us that there are three different ways you can increase the holding power of a clutch: “You can increase the clutch pressure, which is not acceptable because it increases pedal pressure,” Taylor explained. “You can also add a more aggressive disk, but the aggressive disk will make driving the application on the street very difficult. The other way is by increasing the surface area of the disks.” That is what went into the building of the RXT clutch. Because you can only make the diameter so large, McLeod Racing went with a dual-disk system. By doubling up the disks, McLeod Racing made the RXT capable of producing extreme holding power while keeping the pedal pressure soft.
Breaking Apart the RXT
The RXT is a dual disk clutch which means that instead of one clutch disk there are two stacked on top of each other. “The friction material used on the clutch disks is a segmented metallic bronze,” Taylor informed us. This material is used by McLeod Racing because they find it to be very wear resistant against heat. Using the bronze metallic also gives the clutch a good friction point that is aggressive, but not overly aggressive which would making driving the application on the highway difficult.
In between the two disks is a steel plate that withstands the pressure and friction of both clutch plates. The separation plate allows the dual disks to equally displace their holding power which in turn allows the high power of your engine to get through the transmission and down to the pavement. The RXT is technically able to bolt up to a stock flywheel, but we decided to go with McLeod Racing’s 8-bolt lightened flywheel instead. This flywheel is stronger than the O.E.M flywheel, and it is much lighter.
Before installation begins, the first thing to do is determine why you are replacing the clutch. Is it because you want more horsepower? Is it due to clutch failure? For us, we just needed a clutch to handle our horsepower. If you are installing a RXT Clutch on your Mustang, chances are you have high amounts of power likes us. The stock self adjusting quadrant that is on the Mustangs is too weak to withstand this clutch. Taylor confirmed to us, “The stock adjusting quadrant is weaker in an aftermarket clutch, so the self adjusting quadrant is just going to fail. We recommend any aftermarket quadrant.”
The first step to installing the McLeod Racing RXT clutch is to remove it from the box and set up the clutch assembly on a clean bench. The flywheel needs to be checked for any nicks or scratches. If there are any present, the flywheel needs to be resurfaced. Once you have a clean and resurfaced flywheel it is time to mount it. The flywheel is mounted to the engine, preferably using new flywheel bolts. Torque to factory specification.
Once flywheel is installed on engine, you can now remove (6) 3/8” rod nuts from the pressure plate studs. Re-assemble the clutch, checking the disc hubs and floater strap direction. You’ll notice the blue alignment stripes on all parts must line-up. After installing bottom disc and floater plate, use a feeler gauge to check the clearance between them. .020-.025 should just slip in between. The bottom disc should just turn by hand with little front to back movement. This is checked with the flywheel turned up on its edge not lying flat, if too much gap is present (over .025) the floater will push the top disc into the pressure plate, eliminating release. If there is not enough release (less than .020) the bottom disc will drag on the flywheel and floater, and it will not release.
The second disk slides over the spline tool. When the second disk is properly placed, the clutch housing is installed, which also consists of the pressure plate. Once the clutch housing is tightened down, the spline tool can be removed. Torque the three (3) floater strap bolts to 25 lbs max. – red lock-tite is advised. Then torque the six (6) pressure plate nuts to 35 lbs. Max with no lock-tite.
When you are sure the clutch is mounted properly, it is time to re-install your transmission. Use a transmission jack and carefully slide the transmission input shaft into the clutch and slide the splines through the clutch disk. All there is left to do now is hook up the clutch fork to the throw-out bearing and hold on tight!
A Reminder: Breaking in the Clutch
Before any hardcore driving on the street or strip is done, breaking in the clutch is encouraged. When the clutch is brand new, you need to be sure it is grabbing across the full area of the disk. With a few engagements, you should be able to tell. McLeod Racing encourages everyone to drive 500 miles (non-highway) in order to break in the surface of the disks. After that, the clutch will be broken in and ready for any type of driving you can handle.
Installing the RXT gave us the holding power we really needed for our nasty boosted 2003 Cobra. When we climbed into the car to test it out we still somewhat expected the pedal pressure to be high due to the extreme holding power of the clutch. Much to our delight, the pedal went down with ease and the clutch engaged time after time. After our 500 mile break in, we abused the clutch with some hard launches and gear changes, and found it to be very streetable, and yet it had a really nice progressive engagement.
“If you didn’t tell anyone you installed our RXT Clutch, they would think the stock one was in. Until they felt the extreme holding power,” Taylor told us. Being able to have a soft pedal pressure while maintaining the holding power we needed originally seemed like a difficult task. Apparently it was made easy by McLeod Racing.