Replace Original Equipment Clutches With Same Models, New Study Advises

While adjustment-free clutches have bseen available for more than three years, and maintenance-free clutches are now making their way into the marketplace, a great many clutches on the road today lack these recent technological advancements. Consequently, periodic servicing is required.

Unfortunately, a recent study by representatives of the Roadranger field service team at Eaton Corp revealed an alarming industry trend-older model replacement clutches are consistently requiring more service and achieving fewer miles than those used on OEM installations. Since new clutches are shipped to both OEM production and the service market, what could be the reason for the difference?

Improper installation, adjustment, and lubrication practices are part of the problem, warn the Roadranger technicians, and so is faulty selection. To that end, the Roadranger team recommends that maintenance professionals and drivers adhere to the following guidelines when purchasing a "replacement" clutch.

All Clutches Are Not Created Equal Here's how the old school of clutch replacement went: "Just get another one, put it in, and put that truck back on the road." That philosophy simply doesn't work any more. Contemporary new trucks are fitted with a clutch based on field evaluation, driveline configuration, and engine specifications, such as rpm, torque ratings, and operating ranges.

By inputting that data into a computerized simulation program for an OEM installation, the life of the clutch, and the rest of the driveline, is usually maximized. A specific damper design, for example, may be required to reduce harmful driveline resonance in the normal operating range. Therefore, it is recommended that the original clutch always be replaced with an identical service replacement.

Read instructions. Every Eaton Fuller clutch is shipped with instructions in the box. Yet when Roadranger field service professionals are called upon for installation complications, they often find instructions unopened, in the bottom of the box. All technicians should read these instructions-at least periodically.

How Low Should You Go? When starting a loaded truck, always use the lowest transmission gear possible, which may be marked "1st" or "low." Then slowly release the pedal without applying the throttle to avoid adding fuel to the engine and raising its rpm. If the load cannot be moved at this point, the engine should be checked, not the clutch, provided selection and installation were done correctly.

If the engine is operating properly, verify that there is enough reduction to start the load. Also, transmission and axle ratios may not be compatible with the loads and grades that need to be encountered.

Proper total reduction in low gear will reduce wear on the clutch and all driveline components. Using low gear for all start-ups also reduces clutch slip time and shock loads to the drivetrain.

A Few Basics for Older Designs For years of trouble-free clutch service, all that remains is timely adjustment and lubrication-at least for now. As more and more adjustment- and maintenance-free Eaton Fuller clutches enter the marketplace, these two chores soon will be eliminated. Meanwhile, a quick review of adjustment and lubrication basics would appear to be appropriate.

A good clutch adjustment begins by identifying the location of the bearing. It should be positioned 1/2" to 9/16" from the clutch brake. For an accurate reading, stroke the pedal one time and measure the distance. To change the distance, follow the instructions (again) provided with the clutch. This information also may be available on a tag or indicator on the clutch.

After the bearing is set, adjust the truck linkage to allow the clutch brake to squeeze a .010" feeler gauge between the bearing and clutch brake when the pedal is no more than 1" to 1.5" from the floor. Setting the clutch brake position too far from the floor reduces the stroke to the clutch and could cause release problems and reduce brake life.

All that remains is checking the free-pedal distance in the cab. With the pedal in the up position, there should be 1" to 3" of free pedal. The clutch is now adjusted correctly.

As for lubrication, always use a lithium soap base EP (Extreme Pressure) grease with a minimum operating range of +325 degrees Farenheit. It also must meet the NLGI's Grade 1 or 2 specs. Depending on clutch model, design, and features, recommended greasing intervals for on-highway applications range from every 10,000 to 50,000 miles or once per month. For severe-service or off-highway vehicles, recommended intervals are every 250 hours or once per month.

For more information, phone 800-826-4357.