What fleets want from a drivetrain system is really rather basic. They want components that are reliable, have a long service life and are easy to use. This explains the trend toward self-adjusting clutches for manual transmissions, as well as clutches designed specifically to work with automated manual transmissions (AMTs).

AMTs are gaining in popularity for several reasons, the biggest being ease of use through the elimination of pedal effort and shifting. Also, because they are more system-driven than clutch-driven, they reduce the number of parts fleets need to maintain.

Eaton says it has been focusing its efforts on engineering and building durable clutch products to work in harmony with AMTs. First introduced in 2001, the Eaton Fuller UltraShift 6-speed, 2-pedal medium-duty transmission has entered into volume production this year.

The UltraShift 6-speed uses an ASW (AutoShift Wet) AutoClutch. The transmission has two brake pedals, but no clutch pedal, making it fully automated and as easy to drive as an automatic transmission, according to Eaton. It is hydraulically controlled.

For heavy-duty applications, Eaton announced the release of its 2-pedal UltraShift 10-speed fully automated manual transmission. Eaton says the transmission is extremely driver-friendly since there is no clutch pedal. Computer-controlled shifting is done automatically, at precisely the right time.

The DM AutoClutch uses a 15-1/2-in. two-plate design with industry-standard ceramic facing material. It is a dry clutch that is centrifugally actuated. Also built into the system are clutch protection algorithms to minimize clutch abuse.

The UltraShift DM went into LQR (Limited Quantity Release) last month after more than a year of fleet trials. Full release is scheduled for the spring of 2004.

Eaton says another area of focus has been on decreasing drivetrain noise and vibration. Recent releases include a redesigned clutch damper spring for medium-duty applications, and a Soft-Rate damper product for higher torque engines.

Sachs Automotive says fleets want components that offer them the lowest cost per mile of ownership, explaining the trend away from manually adjusted clutches to the maintenance-free, self-adjusting type.

Sachs Automotive is a German-based clutch manufacturing company that's just now gaining recognition in the U.S. truck market. ZF Friedrichshafen AG, a German drivetrain producer, purchased Sachs in 2001. Previously, ZF had entered into a joint venture with Meritor Automotive to build manual and automated manual truck transmissions, including the ZF Meritor Freedom Line. With the ZF Meritor transmission arrangement already in place, Sachs' acquisition of ArvinMeritor's clutch products was a natural extension of its product line.

Sachs notes that having an established field presence at the dealer and fleet level is critical to doing business in North America. That is why ArvinMeritor will continue to provide customer support for Meritor and Sachs clutch products. Manufacturing operations for the Meritor clutch line, however, was relocated to Sachs' existing facility in Mexico City.

Prior to the ArvinMeritor relationship, Sachs was on the brink of introducing a heavy-duty, self-adjusting clutch for U.S. trucks. The clutch is now being field-tested and will be launched later this year. Based on its self-adjust technology used in its European single-plate clutches, Sachs has developed a 15-1/2-in. double-disc cerametallic clutch for the U.S. market. XTend clutches come with a wear life indicator to help maintenance personnel determine remaining clutch life.

Sachs says an important feature of the XTend clutch, designed specifically to combat the problem of clutch drag, is a controlled center-plate release. The use of very flat, symmetrical discs also helps avoid release problems. The clutch incorporates a long-travel-damper disc assembly to protect drivetrains from damaging vibrations. A ventilated cover housing creates air circulation for cooling, which ? decreases wear and promotes long life, the manufacturer adds.

As for how the hotter operating temperatures of '02 low-emissions engines might affect clutches, Sachs says the jury's still out. The company says it's keeping a close eye on engine “excitement” factors and is actively looking at possible changes in clutch dampening design should vibration issues emerge.

FOR MORE INFORMATION, CIRCLE NUMBER ON REPLY CARD:

Eaton Clutch Division 315
www.roadranger.com

Haldex Brake Systems 316
www.hbsna.com

Sachs Automotive 317
www.zfsachs.de

Valeo Clutches 318
www.valeo.com