June 2020

conventional manual transmission in a countershaft design including a dry clutch and was equipped with hydraulic or electric actuators that operated the clutch and changed gears.” ZF Aftermarket has ASG spare parts under its Sachs brand for many vehicles. Kevin continued: “Smart equipped the first two generations of its two- seater vehicle with this drive variant between 1998 and 2015. Other manufacturers who opted for the ASG were Citroën, Dacia, Renault and Iveco. Even the Volkswagen Group equipped its miniature car series and the corresponding Skoda and Seat models with ASG from 2013. “Being a rarer variant, however, although the technology is basically the same in manual transmissions as in vehicles with ASG, there are some striking differences that must be considered as this can take its toll on the clutch during a repair. “In general, automated clutches are stable and less prone to errors. Since engagement is performed by an electronically controlled actuator, operating errors by the driver are irrelevant. Driving at too low a speed is also avoided by the automatic gear change. Nevertheless, even automated clutches wear out at some point or side effects such as plucking or incomplete separation occur.” Precise testing According to Kevin, careful inspection of the entire component is recommended before installation, in case a part being damaged during dispatch: “Particular attention should E ngines are changing, so the clutch and transmission system is being adapted too. Commenting on current trends, REPEXPERT Alistair Mason said: “Manual gearbox cars are still very popular, so there is still a high demand for clutch repairs and replacements. The number of vehicles using self-adjusting clutches continues to increase, as they give the benefits of a lighter clutch operation with a consistent bite point and clamp load. “We are now seeing the use of hydro-electric clutches in semi- automatic transmissions, where an electrical actuator controls hydraulic pressure to the concentric slave cylinder to operate the clutch. A position sensor is fitted to the slave cylinder to give feedback on the clutch position. “The future is in electrically- controlled clutches, which will also help reduce vehicle emissions, allowing the car to coast wherever possible. “Double clutch systems are also now being used by most vehicle manufacturers. The main advantage is the gearchange speed – which can be as quick as 0.08 seconds. Because of this, when accelerating, drivers tend to hold the throttle in one position until the desired speed is reached, and then they lift slightly to maintain that speed. As a result, it is lot easier for the vehicle to run at Lambda 1 to aid emissions control and, because the gearbox is controlled by an ECU, it is always in the correct gear. The dry double clutch system is the most efficient as there is no drag on the clutch.” Maintenance On maintenance, Alistair said: “Generally, the only maintenance required on the transmission system is to change the oil on automatic, wet double clutch and constantly variable gearboxes. This is because the oil becomes contaminated as the clutch wears, losing its lubricating properties as it deteriorates, causing premature 32 AFTERMARKET JUNE 2020 CLUTCH AND TRANSMISSION www.aftermarketonline.net SLIPPING INTO PLACE Below: Automated clutch system from ZF Changing environmental requirements and evolving technology are impacting on clutch and transmission systems wear on associated components, leading to expensive repair bills. “Another area to look at, to ensure gearboxes are maintained properly, is the control unit software. VMs are constantly modifying software to optimise systems and prevent potential problems.” Advice Offering advice for workshops sourcing parts, Alistair observed: “My first piece of advice in this area would be to fit quality parts from a known manufacturer, not simply choose on price. I’d also recommend not ‘mixing and matching’ parts during a clutch replacement. Use all components from just one brand, as they will be optimised to work together. If the flywheel is also being replaced, again use the same brand. We have seen many problems arising from mixing different branded components.” ASG/AMT Kevin Price, Marketing Manager at ZF Aftermarket said there are a number of automated manual transmissions being used across the car parc: “Despite not being adopted as a mainstream solution across the automotive industry, certain car brands installed automated manual transmission (ASG or AMT) systems in significant numbers. “With the automated manual transmission, the automotive industry wanted to establish an alternative to automatic transmissions with torque converters. It was based on the