Gear rattle
Increased gear rattle noise may occur when changing to an aftermarket performance clutch and/or flywheel, including ACT’s products. The most common gear rattle noise occurs when a vehicle is idling in neutral after a long drive or on a hot day. It sounds like a light knocking or growling sound. Gear rattle is an audible noise transmitted from the impacts between the transmission gear teeth. A vehicle engine’s torsional vibrations (momentary angular acceleration) pass through a transmission causing the separation and resulting impact of the gear teeth.
Gear rattle is not to be confused with clutch chatter or out-of-balance vibrations; both of which are conditions mostly felt and generally, not heard. In general, gear rattle is not harmful to the transmission, but can be an annoyance to the driver. It can become a serious concern if misdiagnosed as a transmission or engine problem.
Traditionally, automakers have dampened torsional vibrations by using a clutch disc with a spring-centered design and a heavy flywheel. More recently, however, many have started using a dual-mass flywheel to silence the gear rattle in the transmission. Typically when a dual-mass flywheel is used, the clutch disc features a solid, or rigid-hub, instead of a spring-centered. When changing from a dual-mass flywheel to a solid flywheel, a spring-centered clutch will help dampen the torsional vibrations and reduce, but not totally eliminate, gear rattle noise. Other contributors to increased gear noise include: dual-mass flywheel to a single-mass flywheel conversion, a solid or rigid-hub center instead of a spring center, stronger dampening springs in the clutch disc, increased engine performance modifications or a lighter flywheel or clutch assembly. Gear rattle is a commonly accepted trade-off for performance. Gear rattle noise is not a manufacturer’s defect and ACT will not accept warranty claims because of increases in gear rattle noise.
Prevent damage to the release bearing clip on the Mitsubishi Lancer Evo 8-10 pressure plate
The installation procedure for this type of clutch is very different than for the older Mitsubishi Eclipse or various other Mitsubishi/DSM vehicles. This vehicle utilizes an efficient pull-type clutch that offers more clamp force without adding excessive pedal effort for it to function. However, irreparable damage can occur to the pressure plate’s release bearing clip if improper techniques are used in disassembly and installation of the release bearing. The factory repair instructions must be strictly followed to prevent damage. The release bearing clip is a patented part that is not sold separately, so replacement parts are not available. If damage occurs to the release bearing clip during installation or disassembly, it will not be covered under ACT’s warranty. ACT will replace this clip only if the customer’s original stock pressure plate is provided as a core with a functioning release bearing clip.
Flywheel resurfacing
A smooth and flat flywheel surface is critical for proper clutch operation and longevity. It is extremely important to maintain the proper step in the flywheel, when applicable. A good automotive machine shop will also be able to rebalance the flywheel to ensure that the engine stays smooth and can reach higher RPM without damage to the engine. For special applications, the flywheel may be altered for better performance. For example, racers using a slow-wearing, sintered, metallic clutch disc may change the flywheel step to put the pressure plate closer to peak clamp load because they are not worried about shortening the longevity of the clutch. This job should be left to an expert performance clutch rebuilder, who can properly analyze the characteristics of the flywheel, pressure plate and disc used.
Improved disengagement on Turbo Eclipse, Talon, Laser and Galant VR4
Refer to our previous post if you are having disengagement issues and if you still need to improve disengagement, here are some common areas to examine. For First Generation 1989-1994, first examine the pedal assembly. The lever arm connection to the pedal cross shaft has been found to wear down and decrease the distance the pushrod travels into the clutch master cylinder. Replace the lever arm or pedal assembly as needed. Secondly, examine the throw out bearing for proper lubrication on the guide tube and clutch pivot ball. Thirdly, you may replace the rubber hydraulic line with a steel-braided line for better action.
In Second Generation 1995-1999, these cars have an accumulator cylinder that operates between the clutch master cylinder and the slave cylinder, which is designed to reduce feedback to the driver. Therefore, it increases travel requirements. Consider bypassing this device to decrease the travel requirements and give the driver more feedback. Due to a manufacturer’s defect, the crankshaft design tends to prematurely wear the thrust bearing on some engines. It is commonly referred to as “crank walk.” This does not happen to all vehicles but happens frequently enough to be mentioned. Next, examine the throw out bearing for proper lubrication on the guide tube and clutch pivot ball. Lastly, you can replace the rubber hydraulic line with a steel-braided line for better action.
Release point adjustments to the hydraulic system
On some applications, when an ACT pressure plate is installed, the engage/release point may become closer to the floor. As long as the hydraulics are working properly, this change may be due to flex caused from the added forces placed on the pressure plate and linkage from the increased pressure. A disc that has excessive marcel could also take extra travel to release. In most cases, a small adjustment of the clutch master cylinder pushrod reducing pedal free play will cure the problem. This adjustment is made by screwing the pushrod farther into the clutch master cylinder to allow it to actuate the cylinder sooner. You may also desire to increase pedal travel by adjusting the pedal stop (when equipped). You should never preload the clutch master cylinder. Most repair manuals include instructions and adjustment specifications, which is a great starting point. Clutch pedal travel can also be limited by aftermarket clutch pedals, floor mats or carpet.
Proper use of ACT pressure plates
Advanced Clutch Technology clutches are made to replace the stock units and increase the torque capacity of the clutch. They can be used for many applications. To ensure your safety, follow the recommended RPM limits set by the automobile manufacturer, do not allow the clutch to overheat and conform to all rules set by the sanctioning racing organization. For high RPM or abusive applications, a bellhousing scatter shield should be installed to reduce the chance of personal injury. ACT certifies many ACT pressure plates up to a determined RPM as meeting SFI Specification 1.1 or 1.2. These parts are clearly marked with a SFI serialized certification sticker. Warning: Some ACT pressure plates do not meet SFI requirements because of original equipment gray iron materials and must be considered unsafe for racing, increased RPM or abusive driving. An SFI Specification 6.1 or 9.1 containment bellhousing may be used. ACT accepts no liability for clutches used for racing as many other factors are involved. If you have any questions about an application, please call ACT.
