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Take care of your clutch system and it will take care of you
A vehicle’s clutch connects and disconnects the engine and transmission and dampens unwanted vibrations in a vehicle’s driveline system. If something goes off-kilter, expensive components, such as transmissions, may be affected, and today’s high torque engines put a lot more demand on a truck’s clutch system than previous models.
To their credit, manufacturers have addressed the issue. Many clutch systems are specifically designed to reduce maintenance costs and improve efficiency. Of course, maintenance is still vital, and different types of clutch configurations have different upkeep needs.
Clutch adjustments have always been an annoying necessity for owners of Class 8 trucks. In the past, a driver would notice that there was no free-play in the clutch pedal or that it was getting increasingly harder to put the transmission in first or reverse gear. Into the shop they would go for an adjustment that meant unwanted downtime.
Solo clutches solve that problem. These clutches are equipped with technology that monitors components and auto-adjusts as necessary, using two sliding cams.
The upper cam has a wear indicator tab that protrudes through the inspection hole and follows the exact movement of the cam. (Some technicians call this a “dog tongue” due to its appearance.) The tab shows you when it is time to replace the clutch, but it’s possible to get a false reading. If a vehicle is backing up to a dock and the trailer strikes the dock with enough force, the two cams on the clutch will separate and the top cam will move to indicate a full worn out position. Many vehicle owners and operators have replaced this clutch when it just needs to be reset. A special tool is sometimes required and the reset procedure can be a little tricky, but it is well worth the time. Resetting will help you avoid a costly — and unnecessary — clutch replacement. Of course, that false reading can be avoided if you remember to keep your speed below NASCAR levels while backing up to a dock!
Another area of concern related to clutch maintenance is the clutch linkage. Many people believe that the release bearing located in front of the transmission is the only part of a clutch that needs adjustment. Though critical, it is just one component of a proper clutch adjustment. The linkage must also be checked and adjusted, if necessary. That can be complicated unless your vehicle has a hydraulic clutch system. A hydraulic clutch linkage system on a Class 8 truck mirrors the clutch system on many passenger cars and trucks. The design of the system compensates for any wear on the components. Though an adjustment may still be necessary on the clutch and release bearing in front of the transmission, operators don’t have to worry about the linkage.
Clutch maintenance is the most important way to ensure you get every mile possible out of your clutch. It is critically important to refer to the manufacturer’s maintenance recommendations for your truck’s clutch system. Maintenance intervals are driven by a vehicle’s application and component designs and range from 10,000 miles or one month to 350,000 miles or three years. You may have a very unique system that could go beyond the 350,000-mile range but be sure to follow the manufacturer’s guidelines.
The minimum that you must do is pay attention and avoid exceeding the mileage or time frame for service. When the service interval for a clutch has been exceeded, there is no way to recover from the excessive wear that will occur on the components.
Even better, making the effort to understand your vehicle’s clutch design and operation, as well as its maintenance requirements, will help maximize the life of your clutch and its components, which will certainly improve your uptime.
Homer Hogg, Technical Training Manager for TA and Petro, has worked as a truck technician for more than 30 years. He is ASE Master-certified, a Daimler Certified Trainer and a member of the Nashville Auto Diesel College Hall of Fame.