Ultimate Power Transfer: Challenger Clutches

Remarkably, the clutch on a Challenger is a very simple system that, dependent on construction, is quite reliable and can handle a lot of power.  It all starts with the flywheel which is bolted to the crankshaft of the engine. As the pistons move up and down, the crankshaft and the flywheel will turn in sync, respectively. This is where the clutch enters the fray. The clutch is responsible for harnessing the rotational motion of the flywheel and coupling it to the transmission. 

By using a high friction surface and with adequate pressure applied, a clutch disc will turn with the flywheel and transfer the engine power to the transmission (the clutch hub sits on the input shaft of the transmission), which in turn puts the power to the pavement. 

Applying the clamping force to the clutch is the pressure plate. The pressure plate, a type of diaphragm spring, is responsible for keeping the clutch mated to the flywheel and is also partially responsible for disengaging the clutch as well. It performs the latter in conjunction with the release bearing.

When you depress the clutch pedal on your Challenger, hydraulic fluid is displaced from a master cylinder and is sent to a slave cylinder. The fluid, being incompressible, extends a rod from the slave cylinder that passes through the bell housing of the TR6060 and presses on one end of the clutch fork. The opposite end of the fork moves forward which presses the release bearing up against the center of the pressure plate. This forward pressure on the center of the pressure plate actually causes the spring fingers to bow backward and release the clamping force on the clutch disc, thereby disconnecting the engine from the transmission. This allows the gears to be changed without internal grinding, and the engine to remain at idle without stalling when the wheels aren’t moving.

In the case of modified Dodge Challengers, too much horsepower will cause accelerated wear and tear on a clutch that is not up to spec. Very simply, overpowering the clutch will cause it to slip, which will accelerate friction liner wear through the rotational motion but also through the excess heat that is built up. If the flywheel and clutch are rotating at different speeds (i.e: clutch slipping), a lot of heat will be generated which is detrimental to the life of the clutch. The result is a high revving engine, little forward motion, and an awful burning smell!

If you are adding go-fast performance engine mods, you might want to consider upgrading the clutch in your Dodge Challenger in order to get the power to the ground.

Molded or woven organic clutch: The most common OEM clutch in modern cars is the organic woven type. Woven organic clutches are manufactured with metallic oxides, compounded rubber, and woven fiberglass yarns for increased strength. Molded facings are the most affordable option but lacks the necessary strength to handle high horsepower or high-performance applications. However, most woven organic facings can handle up to 10,000 rpm. Woven organic clutches are affordable, reliable, easy to manufacture, and offers a smooth engagement. For OEM applications and everyday drivability, this is the best option. 

Heavy-duty organic: This type of clutch features a higher level of metallic content than an ordinary organic clutch. This enables the clutch to withstand higher temperatures and better durability in sustained high-performance applications. The heavy-duty organic clutch is ideal for street and track applications. It may be a bit more costly, but it offers enhanced performance with a smooth engagement. 

Ceramic clutch: This type of clutch is manufactured using a careful blend of iron, tin, copper, bronze, and silicon dioxide. Similar to ceramic brake discs, ceramic clutches are designed for racing applications. It can withstand fading even when exposed to excruciating amounts of heat, making it ideal for heavy track use. Price wise, a ceramic clutch is considerably more expensive than a heavy-duty organic clutch. And while ceramic clutches are designed with a higher ratio of static to dynamic friction, the clutch engagement of the ceramic variety can be best described as sudden or abrupt. 

Kevlar clutch: If you need a stronger clutch but don’t need the clunky engagement of a ceramic clutch, the Kevlar clutch is the next big thing. Kevlar is engineered to last three times longer than organic facings while still offering a smooth and streetable engagement action. However, Kevlar clutches demand higher clamping pressures (ergo a high strength pressure plate) and a longer break-in period in order to prevent glazing the friction surface.

There are two general types of clutch discs. A clutch with a solid circular disc is referred to as a rigid clutch disc. However, the twin-disc clutch kit in the 6-speed Dodge Challenger is called a flexible clutch disc.

A rigid clutch is best utilized for racing applications only as it has basically zero shock absorption and thus instantly and harshly transfers power to the transmission.

A dampened clutch disc, like that used on the Challenger, is still more than capable of delivering blistering fast times at the track and comfort engagement on the street. The reason for this is​ the torsional dampener springs in a flexible clutch disc. This type of clutch disc is easy to spot courtesy of the torsion springs and friction discs between the hub and plate of the clutch. As the clutch is engaged, the springs will compress to cushion the sudden surge of rotational forces. This allows the flexible clutch disc to initially absorb the abrupt transfer of power instead quickly modulate it before spinning the input shaft of the transmission. 

There is no exact science to clutch stages. It all depends on the manufacturer of the clutch and what their own independent thresholds are set at. But for clarification purposes, here are four averaged stages that can be found on the Challenger market. 

Stage 1 clutch kits are ideal for street and mild track applications. The clutch can handle in the neighborhood of 15% higher loads than OEM while still maintaining docile engagement and street mannerisms. 

Stage 2 clutch kits offer a higher torque capacity and are great for street racing, drag racing, and autocross applications. While not as smooth as a stage 1, the stage 2 clutch can handle more abuse without major compromise in engagement and streetability. In the Challenger world, expect these systems to hold in the neighborhood of 750 horsepower and will likely use an organic disc. 

Stage 3 clutch kits will usually come with a puck sprung hub disc and can handle even higher torque loads. The aggressive nature of this clutch means it offers higher clamping pressures and an abrupt engagement. Challenger stage 3 clutch packages are typically rated close to 1000 horsepower and utilize a ceramic friction surface. 

Stage 4 clutch kits are strictly for racing applications only. This type of clutch kit will usually come with a solid or rigid clutch in either 3, 4, or 6 pucks. Clutch engagement is tricky and can be a pain to use on normal roads but holding power will be massive - around 1500 horsepower. 

Now, the neat thing about the Challenger and its TREMEC TR-6060 transmission is that it uses a twin disc clutch. While much more expensive than a single clutch system, a twin disk has the advantage of delivering high holding capacities without taking a massive hit on drivability, chatter and overall smoothness of operation. 

It is highly recommend to replace the pressure plate and the release bearing (many owners have trouble with the OEM release bearing with the stock clutch) along with the clutch disc. While it is possible to order just a new clutch disc, most manufacturers sell their clutches as a complete system with disc, flywheel and occasionally a new release bearing as well. This will ensure that each component is designed for the specific clutch to ensure a trouble-free operation. 

In regards to the flywheel, some clutch manufacturers recommended replacing the flywheel as well. At a minimum, it is best to at least have the OEM flywheel resurfaced in order to remove any surface irregularities that developed while in use with the previous clutch disc.

Most manufacturers recommended a clutch break-in period of 200-300 miles, with some as long as 500 miles. During this interval, all they mean is nothing more than driving the car normally, thus no clutch dumps or smoky burnouts until the specified mileage threshold has passed. This will allow the new clutch to embed on the flywheel without glazing the clutch surface.