Clutch makers have put a good deal of effort into designing products that last longer, are driver-friendly and require less maintenance. But no matter how many improvements are made, fleets must still pay close attention to proper adjustment. If the clutch isn't adjusted properly, it will eventually slip, resulting in vehicle downtime or missed deliveries.

Meritor points out that it's important to keep in mind that there are two parts to clutch adjustment: internal and linkage. When installing a clutch, the first step is to set the bearing height correctly; only then are you ready to adjust the linkage to get the right amount of free play. Once the clutch is properly set up, adjustment may be necessary over time to compensate for wear, but it shouldn't be necessary to adjust the linkage again.

But back to the improvements. According to Eaton, its newest clutch designs have greatly reduced or even eliminated maintenance requirements. Eaton Fuller Solo clutches, which are adjustment-free, have an XL (extended lube) option that features a lubed-for-life release bearing. The Solo XL has a wear tab indicator that makes it easy for drivers and maintenance personnel to monitor clutch wear. And torsional vibration, which can be so damaging to other drivetrain components, is minimized by the clutch's seven-spring, VCT (vibration control technology) damper design.

Eaton also makes a Maintenance-Free version of its Solo clutch, available in medium- and heavy-duty formats, that practically eliminates wear on the release pads and bushings, thus eliminating lubrication requirements.

Meritor introduced the AutoJust clutch last fall, a self-adjusting model for the heavy-duty market, including the 2,050 lb.-ft. rating for 600-hp. engines. Internal adjustment for this 15.5-in. two-plate clutch is automatic, although proper initial setup is crucial. An extended-lube release bearing with 100,000-mi. grease intervals is optional. Meritor plans to extend the AutoJust line to medium-duty applications.

Also new from Meritor is a Six-Paddle clutch for the heavy-duty market, providing a 50% increase in friction material over traditional four-paddle clutches. With its longer service life, the Six Paddle is recommended for applications that encounter lots of stop-and-go driving. An extended clutch-adjustment interval is an extra benefit. The clutch, which is compatible with the AutoJust, incorporates the company's LTD (long travel damper) disc design to counteract the torsional vibration that results from today's high-horsepower/low-rpm engines. In fact, Meritor recommends using LTD clutches with any electronically controlled engine that is 10L or larger.

Pull-type Lipe clutches are offered by Haldex Brake Systems for a variety of heavy-duty service applications, including a 15-in. two-plate model for diesel engines up to 600 hp.; a 14-in. two-plate unit for diesels up to 400 hp.; and a 15-in. single-plate for engines up to 350 hp. Direct pressure design eliminates plate force adjustments; stamped steel construction of the clutch cover assembly reduces weight, yet maintains strength.

Valeo addresses the issue of extended wear with its line of 14- to 17-in. single-disc diaphragm clutches for medium- and heavy-duty vehicles. According to Valeo, diaphragm spring technology provides uniform plate pressure and greater plate load as the disc assembly wears. Placing the weight “in the plate, not the cover” lowers operating temperature, which in turn increases the life of the friction material. Maintenance is easier because its clutch doesn't require internal adjustment, and release-system adjustment is a one-person job.

What does the future hold for clutches? The trend that is likely to have the biggest impact on this component is the integration of the clutch and transmission. As Meritor points out, this will result in reduced maintenance and extended wear. Transmissions will be monitoring and adjusting clutches automatically, as well as choosing the appropriate starting gear. Eaton adds that with the clutch and transmission integrated as a controlled system, we'll see models without clutch pedals altogether. In addition, there is a continuous effort on the part of clutch makers to refine friction materials so that component life can be extended even further.

Eaton sees the trend to automated transmissions as providing two primary benefits for clutches. First, they provide protection against starting in the wrong gear, which puts more demand on the clutch and can shorten its life. Second, automation has made it possible to remove the synchronizers from medium-duty clutches and thus add extra friction material.

FOR MORE INFORMATION, CIRCLE NUMBER ON REPLY CARD:

Eaton Clutch Div.
317
Auburn IN
www.roadranger.com

Haldex Brake Systems
318
Kansas City MO
www.hbsna.com

Meritor Clutch Co.
319
Maxton NC
www.arvinmeritor.com

Valeo Clutches
320
Livonia MI
www.valeo.com