Our 5th generation Camaro, dubbed “ZL1UPED,” is brand new to the LSXMAG project car stable. It’s a 2010 Camaro SS that has an LS3 engine stuffed between the framerails to go with the six-speed manual transmission, and has been optioned with the 2SS and RS option packages. Since we’ve added our 5th gen, we have built some big plans for the future, including a ProCharger i-1 supercharger system. In turn, we needed to get the power-handling capabilities up to snuff prior to the supercharger’s installation.
With that in mind, we enlisted the help of our friends over at McLeod Racing to select a clutch package that would work best when faced with the i-1’s 7.5 pounds of boost and 190 rear-wheel horsepower increase.
The Twin Is In
McLeod recommended one of their RXT Street Twin clutches [PN 63055-00-07M] for Project 5th Gen. It’s designed for use by the enthusiast that needs power-holding capabilities up to 1000 horsepower, which is well above where our Camaro will be, but gives us some room to grow in the future. The clutch features a pair of nine-inch discs that, while smaller than the stock diameter single-disc unit, offers greatly improved holding power thanks to a number of notable features.
McLeod’s Bob Scheid explains, “This RXT comes complete with the flywheel, and the neat thing about the RXT is that it has a great ability to hold power while remaining completely streetable. The pressure plate has a little bit lower diaphragm pressure than the stock clutch does, which allows for an easy pedal feel. The pressure plate is a ductile casting, and the straps are heavy duty, but the key to this clutch are the discs.”
The RXT kit includes a pair of full-face, unsprung hub diaphragm-style clutch discs that have a ceramic facing material that’s designed to offer high power handling without killing your leg in stop-and-go driving. Thanks to the ceramic material, clutch engagement is is slightly aggressive, which fits the clutch’s high power-holding capability.
“The ceramic lining is very friendly and has a great coefficient of friction, so we’re able to use the dual discs which gives us four contact surfaces. We’re also able to use a little bit less material on the face of each disc to achieve the holding power. The clutch needs about 5-700 miles of nice, easy stop-and-go driving to get some heat cycles into it, and once it’s broken in the clutch becomes friendlier and friendlier, with smooth engagement,” says Scheid.
In years past, dual-disc clutches often got a bad rap for being noisy; McLeod has put that issue to bed with the RXT series by using a Blanchard-ground floater disc that relies on multiple straps that bolt to the flywheel through the use of specific-height stands. This helps to keep the floater disc in one place, and clutch noise to a minimum.
“In years past, floater plates either rode on pins or some sort of other mechanism to keep it in place, but it wasn’t attached to anything – it floated just like the name implies. By being strapped, they eliminate all of the noise you’d get with a conventional twin-disc clutch. The strapped floater allows the floater to move properly fore and aft as the clutch engages and disengages. One disc is applied just a split second before the other disc, and the floater allows for smoother engagement due to the slight flex in the strap. That slight incremental engagement helps with the smooth feel of the clutch.” Scheid says.
The Wheel Deal
The neat thing about the RXT is that it has a great ability to hold power while remaining completely streetable. – Bob Scheid, McLeod Racing
One of the nice things about this kit is that it’s shipped directly from McLeod with a 13-pound aluminum 168 tooth flywheel, which allows us to pull out the heavy steel stock unit and to keep rotating mass down. Adding the second clutch disc would in most applications increase rotating mass, but the use of the aluminum wheel coupled with the smaller diameter discs brings that mass back down and will actually permit the car to rev more quickly compared to the stock single-disc clutch and steel factory flywheel.
Our McLeod flywheel uses a steel insert. According to Scheid, “Aluminum is a great, strong material that’s lightweight and dissipates heat real well, but the steel insert is there because it has a better coefficient of friction – it’s a better surface for the clutch disc to ride on. Plus, it’s replaceable, so the flywheel is actually serviceable.”
Since we were replacing the flywheel, the decision was made to replace the flywheel bolts at the same time. After speaking with the folks at ARP, the decision was made to order up a set of their Pro Series flywheel bolt kits [PN 330-2802].
These .800-inch-long, 11mm x 1.5 thread pitch bolts are designed specifically for the rigors of performance inside the bellhousing.
The Pro Series bolts are made from aerospace chromoly, feature a flat, 12-point head design, and are finished in ARP’s traditional black oxide. The shank diameter is larger than stock, which helps to provide increased strength and a better register surface for the flywheel. These bolts are designed to be used without a washer.
One item that must be checked prior to installation of the ARP flywheel bolts is that the chamfer on the holes is large enough to accept the radius under the head of the bolt.
The threads should be lubricated with Loctite 242, and the under-head of the bolt should be lubricated with ARP’s Ultra Torque fastener assembly lubricant. Using a criss-cross pattern, the bolts should be torqued to 85 foot-pounds of torque. Following these steps will ensure a trouble-free installation.
Putting It All Together
As always, when it came time for installation, we enlisted the help of Power Automedia’s shop team, consisting of foreman Sean Goude, Dean Jigamian, and Cody Lynn to get the RXT into its new home in Project 5th Gen. They are well-versed in clutch installations, as we’ve done a few over the past couple of years, so our 5th gen was right up their alley.
Disassembly was a relatively simple process, thanks to the lift and fully-equipped shop, but this install can also be done at home on a set of jackstands if necessary – just make sure to get the car high up enough in the air to get the transmission out from underneath.
Prior to removing a single bolt, make sure to disconnect the plugs from the transmission for the reverse lights, along with the hydraulic lines that go to the release bearing. It’s also necessary to get the rear-most oxygen sensors out of the way. Check and double-check that you’ve got everything disconnected before removing the first transmission mount bolt, and your day will go much easier – nobody wants to be fighting a harness that’s still connected when there’s 100-plus pounds of transmission sitting on your chest in the driveway.
Once you’ve got everything dosconnected, remove the bolts holding in the driveshaft bushing, which will enable you to pull the shaft out and set it out of the way. Pull out the starter from the opposite side. From there, the transmission comes out like any other – remove the crossmember mounting bolts, support the transmission with a jack, and take the bellhousing bolts out of the back of the block. Remove the old clutch and flywheel.
Simple so far, right? Here’s where you need to pay a bit more attention. The new clutch and flywheel assembly comes with an alignment mark – you can’t miss it, and this is where the factory has set up the clutch for you already. Pay close attention to how everything is mounted prior to removing the pressure plate, clutch discs, and floater from the assembly, as they are assembled in a specific order, with each disc marked for a specific position.
Follow the directions provided with the kit, and you’ll have a trouble-free installation. Once it’s all installed, reverse your removal procedure, get the car back on the ground, and get ready to break in your clutch. As recommended by McLeod, it should be done with normal street driving (NOT on a chassis dyno) for no less than 500 miles, with traction control turned off if your car is so equipped.
The first thing we noticed when driving with the Mcleod RXT installed was how the pedal feel felt exactly like stock; when pushing the clutch in, Mcleod’s diagram mimics the stock pressure plate’s feel . Since we are running the aluminum flywheel, a little more RPM is required when clutching out the car from a dead stop. Due to the reduction in rotational weight, coupled with clutch material that grips better than stock, that additional engine speed helps smooth that transition.
Once out of first gear, the clutch feels like an OEM unit once again. Shifting between gears is effortless. When we had the clutch broken in, we are able to see how the clutch reacted while hammering the gears…and reacted well it did! The clutch grips the flywheel perfectly with each shift and there’s no worrying about any sort of slippage. With the 1,000 horsepower capability of this clutch, we have tons of room to grow without worrying about changing out for more aggressive discs.
The McLeod directions are very thorough, and they have a full staff on hand in their technical department, so don’t be afraid to call if you have any questions about installation – and enjoy your new clutch!