Clutch Technology

Options for diesel trucks

Published in the August 2008 Issue August 2008

Driving a diesel truck with a manual transmission is a special experience. There is a connection that's made between the driver and drive train. It's a connection where you get to feel every bit of that torque and power as it links directly to the ground beneath you. It's as if you somehow become an integral part of the truck as you engage, disengage, shift and throttle the truck.

On the flip side, there is nothing more frustrating than owning and driving a diesel truck that can't hold its own power. As you pour on the throttle in third gear and expect to take off like a rocket, but instead you feel the engine rpm surge without any effect on the ground beneath you. The control that the clutch and manual transmission give you is satisfying. But for this union to be a happy and satisfying, there must be the right connection between you and the flywheel.

In search of the perfect engagement, we visited South Bend Clutch, just outside of South Bend, IN. South Bend Clutch has been a pioneer in performance diesel clutches as well as other racing and agricultural applications.

Generally speaking, to have a clutch that will hold the increased power we are seeing on today's diesel trucks meant having to live with compromise in the convenience and drivability of your clutch compared to the characteristics of a stock clutch. A clutch that would hold serious power gave you greatly increased pedal pressure, "sticky" or "chattery" engagement and short service life compared to a stock clutch. These days, this is becoming less and less the case.

One of these advancements in clutch technology is in the way that holding pressure is applied to the clutch. South Bend has learned to manipulate pressure plate loads without increasing pedal effort or increasing the clutch size by using a mathematical formula for torque applied by the mean. There is a certain point on a pressure plate where maximum pressure can be achieved using this formula and applying pressure to exactly the right spot on the clutch disc.

Clutch linings also play a large role in holding power. Ceramic-lined clutches have great holding power but can be too aggressive for everyday driving. Kevlar linings are popular in applications with gasoline engines, but behind the torque of a diesel, it gets hot and burns easily. South Bend has been successfully employing a lining that it calls Feramic. Years ago, a customer brought a clutch to them for rebuild from a 1959 Allis Chambers tractor. The material found on the old clutch was different because it was an all-grey metallic lining that was uncommon for a clutch. They had the material analyzed and found that it was made out of pure grey iron. South Bend began to experiment with the iron linings and found that it provided excellent holding power with smoother engagement and longer-lasting service life. They call the lining FEramic, using the Periodic tables symbol for Iron.

South Bend Clutch uses a cryogenic freezing process to treat its flywheels, center plates, input shafts and parts that are performance-oriented. The cryogenic chamber uses liquid nitrogen to cool metals down to minus 310 degrees F. This slows the molecules in the metal almost to a standstill where they become very compact. Then the chamber is brought to 250-plus degrees at a controlled rate so that the molecules align consistently in a uniform pattern. This eliminates stress points and weak spots in the metal. It keeps the discs from warping under heavy-duty use.

South Bend also specializes in dual disc clutches. Dual disc clutches have a large flywheel that house two clutch discs with a center plate between them to allow huge load and power holding capacity with manageable clutch engagement. These clutches are used for extreme horsepower applications, such as sled pulling and racing. Clutch linings are ceramic "button" type pads on the disc face. Because there are two discs to soften the engagement progressively, they are able to use the extreme holding power of the ceramic linings. South Bend also offers triple disc clutches for Duramax applications.

So remember, you've got options and great technology to back them. From stock clutches up to extreme sled pulling clutches, there's everything in between to choose from.


South Bend Clutch

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