Michael Galimi
July 1, 2008
It's no fun when you can't shift your Mustang properly. S197 Mustangs suffer from an ailment in the transmission-the factory hydraulic clutch release.

With the introduction of the sporty '05 Mustang came something Mustang fans weren't used to-a hydraulic-clutch mechanism. Rather than having a cable connected between the clutch pedal and the fork to release the clutch disc for shifting, the S197 uses hydraulic fluid. This makes the clutch silky smooth but can cause problems in high-performance applications. So, we'll ask, is your transmission grinding and hard to shift under aggressive driving situations? If so, the transmission in your modified S197 Mustang probably isn't broken; it may be in the clutch setup instead.

We wanted to throw that out there because there have been a lot of misdiagnosed transmission problems lately. There's an epidemic in the growing S197 community-grinding gears that are hard to engage and disengage. In our search for a solution, we spoke to Justin Burcham of JPC Racing. "Everybody thinks it's a problem with the clutch or the transmission," he says. "It's actually a problem with the hydraulic clutch-release bearing, which will eventually lead to transmission problems. Ultimately, the synchro rings get beat up." Unfortunately, there's no way of knowing how many cars experience this problem.

RAM Clutches produces a heavy-duty hydraulic clutch release bearing. The piston and cylinder are hard-coated for protection.

The grinding and difficult shifting is due to the hydraulic clutch bearing that's used to control the clutch application (either in or out). The pedal isn't connected mechanically as in previous generations of Mustangs, which utilized a cable that connects the clutch pedal to a fork inside the bellhousing. The new cars feature a hydraulic unit that Ford engineers designed to make the Mustangs easier to drive. Much like the brakes, fluid is used to activate a mechanisim; in this case, the throwout bearing that presses on the pressure plate to control release and engagement of the clutch disc (or discs in a multidisc setup).

Since a clutch upgrade is a popular modification, many S197 Mustangs now have an aftermarket unit. Poor performance can result due to the OEM hydraulic clutch release system. "The car will shift fine under normal driving conditions, and the driver won't notice the issue until the engine is at a high rpm, or when racing or beating on the car," Burcham says. "When the driver goes to put it in gear or shift aggressively, the transmission will grind and, at times, not let the shifter go into gear because the clutch is still engaged.

It also features longer travel than stock: 0.510-0.525 inches compared to the stock setup's 0.430-0.450 inches. RAM says this unit is adjustable and compatible with any single- or dual-disc clutch system.

"The factory release bearing was designed for the OEM pressure plate. When you add an aftermarket clutch, there's an increase in centrifugal clamping force on the pressure plate in order for the clutch to attain a greater holding capacity. Thus, the spring that holds the clutch is stiffer, and in turn, the factory release bearing can't deal with the increased load."

According to Mike Norcia of RAM Clutches, the static clamping pressure of the clutch (at idle and low rpm) isn't that much greater than the stock one. The RAM 11-inch clutch has 2,400 pounds of pressure compared to the stock 11.5-inch unit's 2,250. As the rpm increases, however, the centrifugal force from the levers pushes the pressure-plate ring down harder. This is where the extra grip comes from, in addition to the better clutch disc material. Norcia adds, "The position of the lever in relation to the centerline of its mounting point (called the plane of rotation) is such that the upward angle promotes the lever forcing itself outwards as rpm increases. In addition, the centrifugal pressure isn't linear. It starts out shallow, around 5,000 rpm, and basically goes up by the square of the engine rpm from there. At 7,000 rpm, the pressure curve is at about a 45-degree relative angle. At 10,000 rpm, the line would be shooting almost straight up."

The transmission must be removed, so the first step is to unbolt the driveshaft. This car has an aluminum one-piece shaft. We got lucky, as the exhaust system didn't need to be unhooked to get the driveshaft or the transmission out.

To keep up with the ever-growing demands for better performance, the folks at RAM Clutches have designed a heavy-duty hydraulic clutch release bearing. This new product engages and disengages heavy-duty aftermarket clutches, regardless of the manufacturer. "The piston and cylinder are hard-coated for extended life," Norcia says. "It offers increased travel over stock (stock has roughly 0.430-0.450 inches, while the RAM has 0.510-0.525 inches of travel); and it's completely adjustable for use with single- or dual-disc clutch systems."

We drove to JPC Racing, specialists in the S197 arena, to watch as the crew fixed customer Kevin Scott's '06 Mustang. The test vehicle suffered from serious shifting woes at the dragstrip and on the street. The '06 Mustang GT is equipped with a fairly standard package from JPC Racing-a supercharger (ProCharger P1SC), exhaust mods, custom tuning, gears, new clutch, and some other tricks. Output is an impressive 530 rwhp and 460 rwtq-enough to push a full-weight street car into the mid-11s on drag radials. This car was unfortunately stuck in the 12.50s at 122 mph-not due to bad driving but because the driver had to let off the gas completely and shift the car slowly and gradually. The RAM hydraulic clutch release bearing is a welcome addition-now the Stang's owner can finally use all the horsepower that he bought.

The transmission comes out quickly and easily. We suggest you get a bunch of friends to help or use a transmission jack. These Tremec 3650 transmissions are much heavier than the old T5 units common in Fox-body Mustangs.

Installation is straightforward and relatively easy. The transmission is first removed, and the factory hydraulic bearing release is replaced with the RAM unit. The JPC guys did a little grinding inside the bellhousing to properly mount the braided lines and keep them out of the way. A factory vent was opened up a bit so Burcham could inspect the clutch and make sure it was operating and adjusted properly before dropping the car on the ground.

Once JPC's Steve Young completed the install, it was time for a testdrive. A few miles of easy shifting and driving were performed to ensure the unit was operating properly. Burcham then let it rip, and the car shifted flawlessly, without a hint of grinding or any troubles hitting the gears. The week after our visit to JPC, the owner went out to Maryland International Raceway. He ran consistent mid-11s on drag radials and was having the time of his life. Burcham added that he's shifted some of these cars with the RAM unit over 7,000 rpm without a hint of grinding or any other problems.

It's an effective modification to help you have fun with all the horsepower under the hood. This might not be a glamorous tech story with huge power numbers, but it's an important one if you plan on having happy powershifting.

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