With clutches and their ancillaries evolving continually, Rob Marshall finds that technicians should embrace training to keep up, at least.
Tearing the car back down again to investigate why a new clutch is not working as it should is not only frustrating for the technician but it also destroys the job’s profitability. While problems with parts can occur, the main causes tend to be damage, or incorrect fitting. Consider, therefore, that a day spent away from the workshop on clutch training can be recouped very quickly.
The times, they are a’changing…
Blue Print reminds us that clutch changes take longer now than on cars of the past and it can understand why some workshops do not wish to concentrate on such time-consuming jobs. Aisin, a leader in the Asian vehicle clutch market but with its eyes focussed firmly on European expansion, adds that a further reason is the new trend of increased complication, especially with the growing number of specific tools. Asin Europe reminds us that clutch changes are in the top three revenue product lines for garages but technical expertise is necessary to complete the task correctly, a point echoed by Schaeffler that the complexity of the task also means that many adjacent components have to be removed before the gearbox can even be accessed. Valeo concludes that this is why training is key to tackling clutch replacement and gives technicians and garage owners the confidence to justify the invoice value.
Making knowledge work…
Taking advantage of regular training pays dividends, especially as it updates technicians on how and why clutches (including their operating systems) are evolving. ZF Aftermarket’s ZF [pro]Tech training, for example, includes details about the anti- vibration assembly, fitted to the hydraulic lines of a variety of models. Incidentally, the engine and clutch characteristics can cause the slave cylinder to resonate and the steel plates within the anti-vibration assembly distort in order to reduce (or stop) pulses being felt through the clutch pedal.
Knowing about anti-vibration valves is certainly useful but ZF’s Technical Training emphasises that not appreciating how and why torque-limiting valves work can be disastrous and embarrassing for the technician. They are fitted to many popular diesel cars and prevent Dual Mass Flywheel (DMF) damage – although you should note that they are often not replaced if they go faulty, thus emphasising the importance of checking the DMF for condition. In any case, torque-limiting valves work by reducing the fluid flow back to the master cylinder, as the clutch pedal is released. Sachs says that, should a technician be unaware of this, there is a risk that pumping the clutch pedal quickly and repeatedly during the bleeding procedure can introduce excessive fluid into the slave cylinder, which over-extends its piston, which risks tearing the seal lip. Rectifying the issue may mean that the technician has to dismount the gearbox again to replace the concentric slave cylinder (CSC).
While this explains ZF’s reasoning for insisting that you employ either gravity, or low-pressure bleeding methods, bleeding all of the old hydraulic fluid from the system with the old CSC in place is a prudent move. This advantage is that the new cylinder does not have either old, or contaminated, fluid passing through it that risks damaging the seals.
Courses tend to cover not just the clutch but also the Dual Mass Flywheel (DMF).
The most common Dual Clutch Transmission automated manual clutch that you are likely to face is the seven-speed Volkswagen DSG unit (pictured) but do not consider it as a variation of the traditional manual transmission layout. Where a conventional clutch is carried by the flywheel, bolted to the engine, a DCT clutch is carried by and fitted to the gearbox unit. A conventional clutch comes as a three-part kit, whereas a DCT clutch pack is supplied as a pre- assembled component and, generally, is pressed/ installed onto the gearbox input shafts. The double- clutch system’s removal and installation requires additional special tooling and training to conduct safely. Schaeffler is looking to restart its IMI certified double clutch training soon, so keep your eyes peeled.
Training also helps avoid errors that rob ramp time. Blue Print advises any technician not to forget checking the obvious points, including verifying that the factor has supplied the correct clutch kit. Prior to fitting any new components, not only should you research the equipment needed but also its technical data (including torque values). Interestingly, Schaeffler finds that most popular errors result from the service information being ignored. Therefore, should you buy an LUK branded clutch, check for any supporting documents in the REPXPERT portal before fitting it.
Blue Print calls upon technicians not to omit cleaning grease, dirt and old friction fibres from all mating surfaces at the rear of the engine and the transmission bell housing. Schaeffler reports that using a light smear of high melting point grease is all that is necessary on the clutch splines. Never over lubricate and do not use copper slip, which is an anti-seize compound and you might even court corrosion by using it. It also reminds technicians that no lubrication is necessary on metal parts that are running on plastic.
Accidents happen but they can have consequences. Should the friction plate be dropped, you risk either bending it, or damaging the lining. Schaeffler advises that, if you happen to drop the clutch plate, the damage will be obvious in most cases but the company advises you to purchase another clutch to be safe. Dropping the pressure plate can bend the drive straps, causing juddering, or disengagement symptoms, if the damaged part is fitted subsequently.
Getting up to date…
Aside from refreshing delegates with the basics of clutch removal, quality training explains why clutches have evolved – and it is not just to make technicians’ lives difficult. Self- adjusting clutches are one such development, supplied by a number of OEM suppliers that also offer them as aftermarket replacements.
The XTend is Sach’s version of the self-adjusting clutch, the pressure plates of which possess more cut-outs and tend to be constructed from thinner materials. The advantages include reducing weight and inertia within the transmission. This design characteristic explains why incorrect fitting risks not only the cover distorting but also the self-adjusting mechanism being disturbed unintentionally. Sachs recommends the Klann KL-0500-40-k installation tool, which is a worthwhile investment, because it can be used on most other covers, not just XTend types.
When replacing a XTend self-adjusting clutch, depress the clutch pedal fully 5-10 times before the initial test-drive to allow the automatic wear compensation mechanism within the pressure plate to adjust. Sachs also advises extra checks to ensure that the pedal is being depressed fully and that anything that may impede its full stroke (such as an excessively thick floor mat) has been addressed. Clutch slip after replacement may be the consequence of not doing so. Clearly, this operation also highlights the importance of thorough bleeding. Misdiagnosing the clutch kit, instead of the operating hydraulics, will also waste valuable time.
Understandably, high-performance road cars in standard tune can also feature subtle differences in clutch specifications and training will give you an idea about what to expect. These less conventional types highlight the importance of not only studying the installation instructions carefully, before lifting the replacement part from the box, but also using the correct tools. Perhaps one of the most prominent examples is the double- disc clutch, such as that employed in BMW M5 and M6 models, removal and replacement of which necessitates a dedicated tool (BMW part number 83 30 0 495 136).
Sachs points out that it supplies pre-assembled replacement clutches for these models, with cable binders that hold the entire clutch assembly together in a predefined position. As the clutch intermediate disc and pressure plate are balanced relative to each other, they must not be disturbed. ZF Aftermarket’s Sachs replacement clutches possess a reference mark, so you can double-check. Should the clutch pack components fall out as you install the unit to the flywheel, Sachs advises that another clutch will be necessary.
Another special case relates to tuned vehicles. Naturally, any modification that enhances engine output also places extra strain on the drivetrain, which is likely to reduce those components’ lifespans. As mentioned earlier, the arguments for and against solid flywheel conversions are best left for another time but consider that some manufacturers offer not only self-adjusting clutch conversion kits but also clutches for non-standard vehicles. The extensive Sachs performance range is a typical example. You might consider offering as an upsell to not just tuners but also to drivers that tow, plus taxis, certain commercial vehicles and driving school cars. Yet, you do not get something for nothing and a potential downside to such parts being fitted may be higher pedal pressures, or sharper biting points, about which you need to be informed, so you can pass the knowledge on to your customer.
Clearly, the pandemic has affected many in-person training plans. Blue Print, for example, reports that it is investigating several options as it monitors the current situation. Even so, it reaffirms its philosophy of providing as much information and support as possible.
It highlights the ‘bilstein group Infos’, as short advisory notes that accompany the clutch parts in the box. The bilstein group’s ‘Protips’ is a series of technical information sheets that offer practical support with everyday workshop issues. ‘Product Highlights’ include details of component function and common failure reasons, plus more involved ‘Technical Articles’ highlight the diagnostic and replacement procedures. In addition, ‘How To’ videos share best practice information and top tips.
Schaeffler adds that, while plenty of decent commercial systems, such as Autodata and Haynes Pro, provide proper removal and installation guides, they may lack more specific product information. Schaeffler, therefore, highlights its digital information experience, especially the REPXPERT vehicle-specific parts look-up system, which includes fitting instructions, scheduled fitting times, torque settings and service bulletins. Should the REPXPERT app be installed on your smartphone, you can scan the barcodes on the clutch boxes, to access this information more quickly. In addition, Schaeffler’s original popular LuK DMF CheckPoint app is now incorporated within the REPXPERT app. Instructional and installation videos are also available via the training tab on REPXPERT and Schaeffler’s REPXPERT YouTube channel. Throughout 2021, it has also been performing live ‘Tea Break’ training via Zoom, the popularity of which means that more of them are being scheduled. Despite these elearning developments, hands-on training has not been abandoned and Schaeffler hopes to start face-to-face training soon. The company also plans to demonstrate LuK wet and dry DCT systems at AutoInform LIVE, hosted by the GTG Academy in Wolverhampton on the 6th and 7th November.
Valeo also provides technical resources to help you fit its replacement clutches. These comprise monthly-produced Technical Service Bulletins, many of which can be found in the literature, within the products boxes themselves.
The associated fitment diagrams, technical tips, product information and other technical details are also uploaded onto TechAssist, Valeo’s freely accessible technical portal, which is accessed by entering the part number.
Free training webinars are also accessible through TechAssist. These cover the latest Valeo technologies for both OE and aftermarket use and include information on the fitment practices and other useful practical tips, including avoiding warranty issues. Through Valeo’s TechCare program, Valeo Technicians and Trainers produce at least two training webinars every month and the company reports that attendees in the last 12 months number into thousands from 92 different countries. While the previous clutch related webinar was held just prior to this magazine going to print, it can be accessed by logging on to: https://event.on24.com/wcc/r/2867046/8D4 D0429D0C5D8FAC74757A7850F38F3
Valeo also points out that it is also offering additional live training sessions, such as a focus and overview of anti-vibration transmission technology, with sessions being available on request. Should you like to book one of these, AT readers are invited to email firstname.lastname@example.org or email@example.com. In addition, keep your eyes peeled for details about Aisin Europe’s training webinars, planned for later this year.
AVOIDING INSTALLATION ERRORS…
Valeo Service UK shares its top five most common reasons for clutch failures:
- Grease contamination of the friction lining (due to excessive grease placed on the input shaft)
- Incorrect release bearing preload
- Faults in the hydraulic system, such as leaks caused by contamination
- Damage caused to the friction plate spines during fitment
- The friction plate being fitted the incorrect way around