For commercial vehicles equipped with manual transmissions, hydraulic clutch linkage has become popular because it is easier to package into today’s complex vehicle chassis and easier to install during assembly. Many drivers like them as well because they require less pedal pressure to disengage the clutch.

However, when it comes time to replace the clutch, fleets and owner-operators need to ensure they use self-adjusting clutches like Eaton’s Advantage self-adjust or EverTough self-adjust, to ensure they don’t suffer some unintended consequences.

Because a hydraulic linkage places a pressurized fluid between the pedal and the clutch, the free play that a driver can normally feel in the clutch pedal is lost. This means drivers will not be able to identify the reduction in free pedal that normally warns them that a non-self-adjusting clutch requires servicing or an adjustment. Failure to recognize these traditional warning signs can lead to premature wear or failure of the clutch.

With a mechanical linkage, the driver can feel the reduction in free pedal as the clutch wears. This reduction in free pedal provides an indicator to the driver to bring the truck in to have the clutch manually adjusted.

With a hydraulic linkage system, because the free pedal is totally eliminated, the driver doesn’t have the same level of feel. So the driver has to be very good about bringing the truck in for service regularly and having that clutch wear checked to see if it needs to be adjusted, which often doesn’t happen.

Losing touch with the clutch can have some undesired outcomes. A manual-adjust clutch that isn’t re-adjusted as required can suffer a shortened service life.

As it goes out of adjustment, the clutch yoke can begin to make contact with the clutch cover and do serious damage to the clutch and the release mechanism. Or, the clutch can begin slipping and that heat can damage the clutch so that a new clutch is needed. The flywheel could be damaged as well if it gets too hot.

Typically, a manual-adjust clutch will need to be re-adjusted a minimum of 13 times through its lifecycle. If just one adjustment is missed, the clutch may have to be taken out of service well before its intended lifespan.

This is why Eaton strongly suggests using self-adjusting clutches such as the Advantage self-adjust or EverTough self-adjust on trucks with hydraulic and mechanical linkages. The truck OEMs, in most cases, now offer these self-adjusting clutches as standard equipment on manual transmission-equipped trucks.

However, it’s equally important that the appropriate, self-adjusting clutch is chosen for replacement in the aftermarket. There are benefits to using a self-adjusting clutch, not the least of which are the reduced maintenance requirements and their associated costs. A clutch adjustment can take anywhere from 15 to 30 minutes to perform. Extrapolated over the 13 re-adjustments a manual-adjust clutch will typically require, the maintenance savings alone can be significant.

And that’s assuming an operator is taking the vehicle in for a clutch adjustment whenever it’s needed - something that’s trickier to do when a hydraulic linkage is paired with a manual-adjust clutch.

If someone is very good about doing their adjustments on their clutch, the savings is really the labor of doing those adjustments.  But in many cases, the adjustments don’t get done, and that’s an increased risk with hydraulic linkages and that’s why the Advantage self-adjust and EverTough self-adjust have so many benefits.

As far as maintenance is concerned, the Advantage self-adjust and EverTough self-adjust clutches, like Eaton’s Easy Pedal manual-adjust and EverTough manual-adjust counterparts, still require greasing of the bearing and sleeves.