Adopting best practices can keep the clutch in gear

Customers understand repairs can be costly, but avoiding comebacks will help you repair clutch problems better.

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A vehicle's clutch is one of those components that doesn't get a whole lot of attention until the time comes that it isn't working properly. In that respect, clutch maintenance often is forgotten about just like any other vehicle maintenance. However, when a clutch malfunctions, it often cannot be ignored because the vehicle suddenly becomes difficult or impossible to drive. And while the problems can sometimes be easily fixed, in many cases it results in a costly, time-consuming repair.

Customer satisfaction is built on accurate diagnosis and repairs. Customers generally understand that repairs can be expensive, but they also expect that they should not have to bring the vehicle back anytime soon for the same problem. From the technician's perspective, clutch jobs require a good deal more time than many other repairs and tie up lifts (especially FWD jobs). For these reasons, it is advisable for technicians to adopt a set of clutch service "best practices" that will maximize productivity and limit the possibility of comebacks.

Verify the Concern

Accurate diagnosis always begins with a thorough customer interview. Ask the customer what the problem is and under what conditions it takes place. Have the customer take you for a road test in the vehicle (if it will move) and make certain you fully understand the nature of the complaint. This may also give you a chance to observe driving habits that have contributed to the problem. When a customer comes to you with a clutch problem, it can often be easily verified and will likely be in one of the following five categories: hard pedal, poor release, noise, chatter or slipping.

The good news for the customer is all of these complaints can be caused by something other than the clutch itself. In other words, a repair may be possible without the expense of having to remove the transmission/transaxle assembly.

Diagnosis

When diagnosing a clutch concern, start by assuming the clutch assembly is OK. What else could be causing it to malfunction? The technician's initial inspection will be guided by the nature of the customer complaint.

Hard pedal – excessive effort is required to move the clutch pedal. Look for binding or sticking in clutch release components, or possibly a restricted hydraulic line. Disconnecting linkages may help narrow the source of the problem.
Poor release – the clutch will only disengage partially or not at all. Turn off the engine and try shifting into first and reverse. If it shifts fine with the engine off but not when the engine is running, you have a clutch release problem. All clutch release components should be inspected for proper operation and adjustment, which include pedal bushings and brackets. Make certain that no leaks exist in the clutch hydraulic components and that the system is bled properly. Consider the possibility that the fluid in the clutch master cylinder has been contaminated (power steering fluid, maybe?).
Noise – strange noises are generated during clutch release or engagement. Try to get a sense of the kind of noise and where it is coming from. Noises from inside the vehicle will be related to the pedal mechanism. Outside noises could be caused by worn driveshaft components or engine mounts. Improper clutch adjustment can play a role here as well.
Chatter – the drivetrain jerks or grabs during clutch engagement. Misaligned, loose or broken mounts can cause this. Check the mounts for the engine and transmission, as well those for other drivetrain components (including RWD or 4WD axles).
Slipping – engine speed "flares" during acceleration, or in the worst case, the car won't go anywhere. Slipping can be caused by improper clutch adjustment or malfunctioning release components. The critical issue here is how bad was the clutch slipping and for how long? The clutch may still have to be replaced, even if the source of the problem was something other than the clutch itself.

If these external factors have been ruled out as the root cause, you can start thinking about replacement of the clutch assembly as a fix for the problem.

First Steps

Once you have decided that the clutch assembly must be repaired, there are a number of items that should be considered as you prepare an estimate for the customer. First, you will be replacing most of the clutch components while you are in there. Replacing the clutch is just too much work to gamble on not replacing relatively cheap parts like the release (throwout) bearing. If one is available, the best value for your customer is probably to order a clutch kit with everything included.

An estimate may also include an engine rear main seal if the vehicle is a high-miler or if you suspect the seal may already be leaking. A new clutch cable is a good idea if the vehicle is so equipped. The customer should also be informed of the possibility that other items may require attention once the transmission has been removed. One example is aluminum engine blocks where the bell housing bolt holes are on the verge of being stripped out.

It would also be wise to take a quick look at the service information (A clutch is a clutch, right? Wrong!) and see if there are any special considerations for the vehicle in question. Here's a possible surprise — special tools being needed to remove and reinstall the pressure plate in a self-adjusting clutch. In the interest of productivity, it pays to do your homework and know what will be involved before the serious work begins.

Clutch Repair

As mentioned earlier, most of the clutch components will be replaced as part of the repair. One area that will require some judgment on the part of the technician is flywheel condition.

There are three possible outcomes for the flywheel: use it as is, resurface it or replace it. If there is only light wear and few heat checks on the flywheel surface, you may be able to leave it in place and only "rough up" the friction surface with a sanding disc. If the flywheel has seen some punishment, you will have to take it to the next level.

While the flywheel is still in place, do a quick check of crankshaft end thrust and flywheel runout with a dial indicator and compare to specs.

Before reinstalling the flywheel, use a small, flat whetstone and penetrating oil to lightly polish the surface where the flywheel mates with the crankshaft. Rub the stone over the surface looking for high spots or nicks that could cause flywheel runout. These will appear as shiny areas as the work progresses.

It is also a good idea to conduct the same treatment on the crankshaft mating surface. Be certain to clean any remaining grit from the surfaces before reinstalling the flywheel. Be aware that some installations require that sealer be applied to the flywheel bolt threads to prevent engine oil leakage. Once the flywheel is installed, get out your dial indicator and do a final runout check to confirm the accuracy of the machine work and the installation before mounting the clutch components.

The pilot bearing (if equipped) is the least expensive component in a clutch assembly, but plays a major role in its proper operation. Replacement of the pilot bearing is not optional...just do it and buy yourself some peace of mind. Nothing like a comeback related to a $5 part!

While you have the new clutch components available, take the clutch disc and install it on the transmission input shaft. Move it back and forth on the splines, looking for any damage that could prevent the clutch from releasing properly. The release bearing should also be checked to confirm that it is a correct replacement. Double check for wear of the bearing retainer (the surface that the release bearing slides on) and then lightly lubricate it before installing the release bearing.

There are a number of places in the clutch mechanism that require lubrication to assure proper operation. The emphasis here is on light lubrication; excess lubricant has the potential to make its way onto the clutch lining and cause slipping or even grabbing. A high-temperature grease should be used on friction points such as the clutch disc splines, release bearing support and release arm pivot. One place where you should not use grease as a lubricant is a pilot bushing. Pilot bushings are made of a porous bronze material and should only be lubricated using SAE 30 motor oil.

The remainder of the clutch components now can be installed. Be certain that the clutch disc lining and all friction surfaces are clean using an alcohol-based solvent. Make sure that the clutch disc is installed with the correct side facing the flywheel, and that it is aligned with the pilot bearing. Things go well here if you use the plastic arbor that comes with most clutch kits. Install the pressure plate, tightening the bolts evenly and torquing them to specification.

Before installing the transmission, do a careful inspection of the bell housing mating surfaces to ensure that they are clean and undamaged and that all dowels and locator pins are in place. Lift the transmission and continue to support it until the bell housing has been installed flush with the engine block and a number of bolts are holding it in place. Do not allow the transmission to hang unsupported as this will damage the clutch disc assembly.

Clutch Bleeding

Once the transmission is in and all the related parts have been reinstalled, a final step will be to bleed the clutch hydraulic circuit. In some cases this can go really easily, in others it can be your worst nightmare. The easy ones can be gravity bled; just open the bleed screw and make sure that the reservoir stays full. The worst clutch bleeding problems are on vehicles where the hydraulic components are mounted at an angle (i.e.; clutch master cylinders in Ford Rangers and Explorers). In these cases, it may work best to try a reverse fluid injection strategy.

Adopting a set of "best practices" when performing clutch service can increase productivity, minimize comebacks, and enhance customer satisfaction. Ultimately, this translates into repeat customers and increased profits for your shop.

Tony Martin is an assistant professor of automotive technology at the University of Alaska Southeast in Juneau, Alaska. He holds Canadian Interprovincial status as a Journeyman Heavy Duty Equipment Mechanic. He also has 18 ASE certifications, including CMAT, CMTT, L1 and L2.