Clutch Improvement – McLeod Racing’s RST Twin-Disc Unit Upgrades This 2011 Mustang GT
Manual transmissions, late-model Mustangs, and poor clutch performance are synonymous with one another. When equipped with the Getrag MT-82 close-ratio six-speed transmission, the 2011-newer Coyote-powered Mustang suffers from many maladies once the RPM levels are turned up past the 7,000 number on the tachometer. Searches of Mustang forums and Facebook groups populating every corner of the World Wide Web show thousands of complaints from car owners about being locked out of gear by clutches which won’t disengage, which is caused by a variety of issues.
There are a number of solutions to the sticking clutch concern. When I experienced the same problem myself in my supercharged 2011 GT, I went searching for information. Answers I found included changing the hydraulic line to a stainless braided piece (which I did, and didn’t help), to a separate hydraulic reservoir (didn’t do this one), a transmission fluid change (did this, with marginal improvement), and then to a new MGW Race Spec shifter (this change provided incredible improvement and is a must-do mod, especially with regards to shift feel and consistency, but it didn’t eradicate the lockout issue completely for me), and finally to the ultimate fix, a new clutch—which is the focus of this article.
McLeod Racing came to the rescue with one of their RST organic-faced twin-disc clutch kits, along with a new lightweight steel flywheel and hydraulic release bearing.
Regardless of all the other changes I made trying to cure the problem, the simple fact is that the reason for clutch disengagement problems in Coyote-powered Mustangs is failure of the Valeo original-equipment clutch to disengage at high RPM levels. In many cases, Coyote owners are pushing these engines to 7,500 rpm and beyond, and the OE clutch assembly simply can’t handle the abuse heaped upon it by enthusiastic Mustang owners seeking to wring every last drop of performance out of their cars by no-lift powershifting and living by the Mustang owner’s adage of “drive it like you stole it.”
But when parts don’t operate as expected, it becomes extremely frustrating. The McLeod Racing RST clutch makes those issues a thing of the past. It installs with a minimum of muss and fuss, and when paired with the company’s lightweight billet-steel flywheel, even improves performance noticeably by reducing rotating weight and allowing the engine to move through the RPM band more quickly.
The RST Street Twin clutch [PN 6912-25] is designed to be a reasonably-priced, yet serious performance upgrade, and with a street price of $752 for the clutch assembly it definitely falls into that realm for the average enthusiast. McLeod has engineered the design to support 800 horsepower easily, yet through the use of a diaphragm-style pressure plate and smaller, lighter organic discs, the assembly actually engages and drives more easily than the stock clutch design. Even though I had read about this in several online reviews prior to installing the clutch, I was still surprised once we installed it at just how smooth engagement was and how light the pedal pressure was compared to the stocker.
“We try to replicate the factory clutch as closely as possible,” says Lee Kilcoyne, McLeod Racing’s Senior Technician for Product Development.
“We set those up here, check them, and test them. Ideally we’re looking for a release point somewhere between one-third and halfway off the floor. We use a marcel disc on the bottom of these so they are easier to modulate for the street driver. The learning curve depends on the individual driver. If someone has been driving a clutch car for their entire life, they’re going to get into the car and it’s going to drive more or less the same. Whereas if they’re just getting used to a manual transmission, the lighter clutch will be slightly grabbier and it’s something they’ll have to get used to. We recommend when breaking them in, that people drive them like they drive every day.”
The RST clutch assembly includes the pressure plate, a pair of friction discs, the strapped, Blanchard-ground steel floater plate, an adapter ring to mount the assembly to the flywheel, and the correct 23-spline, 1-inch pilot tool along with the necessary nuts, washers, and dowel pins for installation.
As the clutch discs in the RST are 9 11/16-inches in diameter compared to the 11-inch diameter of the stock clutch, the adapter ring is required to mate everything up properly. McLeod engineered the ring to match the flywheel with the reduced-diameter pressure plate; the floater plate also mounts to the adapter ring, ensuring that the clutch is quiet in operation.
“The smaller diameter means the clutch has a lower moment of inertia,” says Kilcoyne. “With the weight closer to the center of the flywheel the engine will rev more quickly.”
The RST clutch and flywheel assembly is approximately 43 pounds installed, compared to the stocker at slightly over 47 pounds complete.
In this particular application, the RST does require a new flywheel for proper operation, as the clutch material diameter is larger than the friction surface on the stock flywheel, so that expense must be taken into account. Many RST applications do not require a new flywheel, though.
I chose to use McLeod’s SFI-approved, lightened steel flywheel [PN 463458] instead of their billet aluminum piece; on a heavy street car like mine, I felt that the heavier steel piece would help retain some of the smooth drivability characteristics I’ve come to expect. Plus, when I drive this car to work (33 miles one way) it’s through a lot of stop-and-go traffic with plenty of clutch cycles, and I didn’t want to have to deal with any potential chatter caused by the incorrect flywheel choice for my intended usage requirements.
The McLeod Racing hydraulic release bearing [PN 1200] is quite simple—it’s a heavy-duty stand-in for the factory Ford unit and is designed to bolt right into place on the factory transmission and provide flawless operation. I also added an ARP flywheel bolt kit [PN 156-2801] and a new pilot bearing from Ford Racing [PN M-7600-B] while the transmission was out—these two items are cheap insurance.
Specific notes: The company does not recommend the RST clutch to be used in a competition environment. So if you’re planning to hit the road course or dragstrip every weekend, then stepping up to the company’s ceramic-faced RXT clutch assembly should be on your radar. I take this car to the dragstrip three to four times per year at most, so I’m willing to take my chances. The ceramic-faced RXT can be unkind to completely-stock transmissions if there is already internal damage, but if the transmission is in sound working order prior to its installation, it is the most applicable choice for a car in serious competition circles. And if you’re making 1,000 horses to the tire and still trying to race a six-speed, chances are you’ve already made internal transmission upgrades to withstand the power level where an RXT is most effective.
In my particular case, I had to weigh the options of how this car is used 99.5-percent of the time compared to the half-percent of the time I’m at the racetrack and determine what was most important to me. I feel the RST is the best overall choice for my application.
With the parts selected, it was time to get to work putting them into the car. I enlisted the help of longtime friend Brandon Abbott of Midnight Auto in Feasterville, PA to tackle the install process. Follow along with the photos and captions as I detail the specifics of knocking out this job in a few hours. Of course, the lift is helpful, but this could have been done on a set of jackstands if necessary—it just would have taken us a lot longer.
The underside, at the beginning. Thankfully Ford provided enough room to work underneath the car without having to remove the headers to get the transmission out of the car. With the V-bands located throughout the exhaust, removal of the H-pipe was a snap.
The factory k-member brace needs to be removed for access; four 15mm nuts and this is pulled right out of the way. There are a number of electronic plugs on the transmission for items like the speed sensor and oxygen sensor connections which need to be disconnected for transmission removal.
It’s always a smart idea to mark the location of the driveshaft flanges on both the pinion yoke and output shaft of the transmission to prevent unwanted vibration upon reinstallation.
We weren’t sure if we’d be able to snatch the transmission out of the car with the shifter attached, but once I removed the console, I thought there might be just enough room—which there was. I did have to disconnect the linkage rod so I could push the shifter handle all the way forward to clear the body as the transmission moved rearward, but that’s it.
With the exhaust, driveshaft, shifter, and transmission mount disconnected, Abbott employed his longest extension to get the top two bellhousing bolts out of the back of the engine block. Alternatively, these can also be accessed from the top side of the engine bay. Removal of the starter takes a few minutes as the top bolt is notoriously difficult to remove, but once that’s out of the way, the rest of the process is relatively painless…
…With the exception of the hydraulic line’s quick-disconnect. It’s not so much that it’s hard to get out, you just need to take extreme care not to lose the retaining clip—I know because we had one of these shoot across the shop when we replaced the line with the stainless braided piece a while back. It’s not easy to get to with the transmission in the car, but thankfully we had just enough slack in the line to drop the transmission down far enough to get the clip out. Reconnecting it to the release bearing is another story altogether, and required the use of a set of bent-tip needle-nose pliers and careful persuasion to snap it back into place. But that’s about the most difficult part of the entire clutch installation.
With all of the fasteners removed, the hydraulic line disconnected, and the shifter linkage freed up, Abbott pulled the transmission out of the car rather easily. Removing the stock clutch revealed the reluctor wheel on the back of the crankshaft. Many people have previously mentioned having to do a crankshaft relearn using a handheld programmer. I must have gotten lucky, because once we buttoned everything back up, I’ve driven the car approximately 800 miles so far with no issues or codes thrown.
The stock clutch upon removal. Honestly, I was expecting to see much more wear than I did – this thing has been through 50,000 miles of abuse—31,000 with the original owner and then mine, which included the addition of 200-plus wheel horsepower. But you can still see the machined grooves on the pressure plate and flywheel, and the friction material wasn’t even wrecked. It was only a matter of time, though, given the power the car makes and the stuck clutch syndrome I’ve experienced.
Removing the pilot bearing for the new Ford Racing part. Proper tools make all the difference in the world—this step of the process was completed in just a few minutes.
McLeod provides explicit directions on how to set up the clutch properly. We ran through the process on the bench just to ensure all of the parts and pieces lined up, the fasteners torqued properly, and there were no issues. Dowel pins are installed into the flywheel, the bottom disc is laid into the flywheel, and finally the adapter ring and floater/top disc/pressure plate are placed on top.
McLeod provides an extremely helpful video that details the process as well:
Flat washers, lock washers, and then nuts are installed prior to the torque sequence of 1-7-3-9-5-11 o’clock to 25 ft-lb and then 35 ft-lb in the same pattern. This ensures the lock washers are flattened and the diaphragm finger height is correct, as checked with a straightedge.
Installing the flywheel to the crankshaft. ARP specifies that all fasteners must have the supplied Ultra Torque lubricant applied to the underside of the bolt heads, and Loctite #243 medium-strength threadlocker applied to the threads. Set the torque wrench to 70 ft-lb and use a star pattern until the fasteners are secure.
We placed the pilot tool into the crankshaft and then the bottom disc into position before installing the adapter ring onto the dowels. The old star pattern comes into play here also, as the adapter ring is fastened to the flywheel with 35 ft-lbs of torque. The rest of the install process is as it was on the bench.
One helpful tip provided by Kilcoyne is to assemble the clutch around the pilot tool, then give the pilot tool a one-quarter turn to ensure the splines in both discs are lined up; this ensures that when the transmission is hoisted into place the installer isn’t fighting the discs to get them to line up with the input shaft.
“Guys are tempted to start pulling the transmission in with the bolts. If something’s not lined up right and you drag the input shaft through the hubs and bend one of the discs, then you can run into release issues or damage the unit. The most extreme cases we’ve seen have had guys break ears off the engine block trying to draw the transmission in,” says Kilcoyne.
One step which often gets overlooked: a quick cleanup of the input shaft end before hoisting the transmission back into place.
Three bolts fasten the release bearing to the transmission.
From here, reinstallation is the reverse of removal. The hardest part was getting the hydraulic line hooked back up, and it took a few minutes to wiggle the top two fasteners into the block correctly, but that was it. Fill up the master cylinder—don’t spill any brake fluid on the paint—and pump the brake pedal over and over and over until you have a firm pedal, then head out for a test drive. It takes a good 200 strokes of the pedal or more until it firms up and bleeds the air out of the system; I lost count.
The Driving Impression
My initial thought was ‘Did we install this correctly?’ as the pedal effort was so light compared to the stock clutch it was almost unbelievable to me. The release point also changed; previously, the stock clutch grabbed right off the floor, and the RST grabs much higher in the pedal stroke. This presents two new things when driving the car; first, I had to re-train my muscle memory with respect to accelerator position and clutch pedal position, but secondly—and more importantly—it means that the clutch pedal isn’t required to go to the floor when shifting, so at the track I can theoretically tap the pedal to make gear changes instead of having to follow the entire arc.
A serious change was noted in drivability to the positive side: the reduced mass of the flywheel combined with the reduced rotating weight from the clutch manifested in quicker acceleration and climb through the RPM range. The car is much more enjoyable to drive now—it’s amazing to me that something so simple could make such a difference in the car’s drivability.
We performed this swap the week prior to the NMRA’s event at Maple Grove Raceway, where I planned to run in the True Street class like I did last year (you may remember this article) and finally nail down the 10-second quarter-mile pass I’ve been searching for over the last year-and-a-half since I installed the ProCharger on the car. I drove it to work every day in between the install and race day; I spend a lot of time in stop-and-go traffic—the perfect situation to ensure the clutch discs are seated in properly.
Sadly, the event was rained out and I didn’t get to run the number. My sole test pass didn’t include any help from the traction gods; although the car went 127 mph shifting about 500 rpm low, it also spun off the line, which meant no 10-second pass.
I can say one thing—the clutch grabs incredibly hard compared to the stock unit. I can’t wait to get a full session in and see what the car is capable of now!
Photo: MIke Galimi/NMRA