Heavy Duty
Installing McLeod’s RXT1200 clutch in an 800-plus-horsepower GT500
By Steve Turner
Photos courtesy of VMP Performance
The Shelby GT500 presents a daunting challenge for a clutch. These are heavy cars that produce tons of torque. When you bolt on a set of sticky tires, raise the rpm to the moon and dump the clutch as many owners are wont to do, and the clutch is stuck between the rock we live on and a really torquey hard place.
That’s definitely the case when it comes to VMP Performance Business Manager BJ McCarty’s 2007 GT500. Since the day he bought it, this Shelby has split time between the street and numerous trips to the drag strip. Over the years it’s been upgraded with numerous parts, including VMP’s highly effective Gen2 TVS supercharger upgrade.
As a result, BJ’s normally rolls around with over 700 horsepower and can put down over 818 horsepower and 790 lb-ft of torque when tuned up with E85. Though BJ is often distracted by tweaking his other car—a 2015 EcoBoost Mustang dubbed The EgoBoost—that doesn’t mean that his GT500 doesn’t need some TLC from time to time. Besides, when your car is named Christine, it’s probably a good idea to keep her happy.
[video=youtube;W_zwnZU3cqU]https://www.youtube.com/watch?v=W_zwnZU3cqU[/video]
When it was time to upgrade the his existing McLeod RXT clutch, which had about 40,000 hard miles on it, BJ needed something that could corral the huge torque that his VMP Gen2-boosted 5.4 puts down, but not make his driving experience too unpleasant for the street. Those criteria ultimately led him to select one of McLeod Racing’s new RXT 1200 twin-disc clutches (PN 6918-07HD; $1,993.75).
“It has literally made two passes since we put it on E85 and on the second pass it spit a differential. It now has a spool, a fresh set of Ford Performance gears, and the last thing I wanted to do is have the clutch fail in the middle of our narrow window of decent weather and have to go through a break-in period then,” BJ explained. “So, I talked with McLeod and we discussed using the HD unit as opposed to the one I've been using.”
“Upon removal we saw that there was probably another 10k of material left under normal use, but certainly less than that with the abuse Christine is used to,” he added. “We were correct in assuming that it would probably go south on us midway through our season.”
While he was at it, BJ elected to install some upgrades along the way. He added a fresh slave-cylinder/throw-out bearing assembly to ward off any potential failures due to wear. He also added a heavy-duty hydraulic clutch line from Stifflers. It is better suited to survived the heat put out by his high-horsepower engine and offers the added benefit of improved clutch-pedal feel.
We followed along with the highlights of the installation, which is a straightforward, remove-and-replace operation, so we hit the highlights of the process in case you are considering the same sort of swap. If you need even more detail on the installation consult the detailed instructions and McLeod also put together this handy install video…
[video=youtube;rWX6zKIGLaI]https://www.youtube.com/watch?v=rWX6zKIGLaI[/video]
VMP Performance’s BJ McCarty puts plenty of street miles and drag strip laps on his 2007 Shelby GT500. When it was time for a clutch upgrade, he chose McLeod Racings’ RXT 1200 Twin Disc Clutch (PN 6918-07HD; $1,993.75), which is designed to support up to 1,200 horsepower while retaining streetable actuation.
BJ and the team at VMP Tuning got started by removing the stock driveshaft, transmission, clutch and throw-out bearing. Then they cleaned the inside of the bellhousing to remove thousands of miles worth of clutch dust. Once the trans was squeaky clean, they lubricated the input shaft to prep it for the reassembly process.
If your car has more than 10,000 miles on it, BJ recommends that you replace the factory slave cylinder and throwout bearing assembly with a fresh unit. BJ’s stocker (right) sure looks like it has seen better days.
BJ bolted up the new slave cylinder/throwout bearing assembly, tightened its two fasteners to 15 lb-ft and plumbed its hydraulic line.
Since BJ’s car has racked up over 61,000 miles, BJ also opted to replace the pilot bearing if you don’t own the puller/slide hammer to facilitate this swap, you can rent one. Once you remove the old one, just tap the new one into place.
To prep the RXT 1200 for assembly, remove the cover, disc, floater and bottom disc.
Remove the stock flywheel and bolt up the new McLeod unit, torquing the fasteners to 59 lb-ft of torque. Using the alignment tool, install the bottom disc, the floater ring, the top disc and the pressure plate. Make sure the flywheel side of the bottom disc is facing the flywheel. When you install the floater, torque the three 5/16-inch strap nuts to 25 lb-ft.
Then use a straight edge across the pressure plate to ensure none of the fingers are above the opening. Make sure you have the discs aligned and that they move freely when you spin the alignment tool by hand. If so, you can torque the pressure plate to 25 lb-ft in a star pattern, then to 35 lb-ft when the lock washers are crushed.
Once the installation is complete and the fasteners are torque the clutch should have .020 to .025-inch of clearance at full clutch release. Before reinstalling the transmission, BJ drained the transmission fluid and replenished the Tremec T-6060 with 3.8 quarts of Mobil 1 RTF.
The factory hydraulic clutch line can be affected by exhaust heat. The heat may damage it or simply cause it to expand and contract, which results in inconsistent pedal feel. BJ opted to upgrade his line with a stainless-steel braided unit from Stifflers.
With the transmission out of the car, it’s easy to click the new line into the factory fitting and plumb it to the master cylinder once you have reinstalled the transmission. Be sure to refill and bleed that brake system to remove any air bubbles and you are ready to drive. Just be sure to break in the clutch as prescribed in the McLeod instructions before you drive your GT500 in anger.
