By Bob Dowie
Clutch replacement does not have the prestige of driveability diagnostics, but at times, it pays better. Some shops turn away clutch replacements in fear of comebacks and lost productivity. But, clutch replacement offers the shop opportunities to sell additional services that might slip past the bottom line.
We once had a Mazda Protege sedan come in our shop (Village Auto Works, Chester, NY) with a slipping clutch. In this article, I’ll review the important steps that must be performed to diagnose and sell the job to achieve a successful, profitable service for you and a positive repair experience for your customer.
Clutch problems will present themselves in a couple of ways. The most common and easiest to diagnosis is a slipping problem. But don’t assume that your customers will always know that the problem is a slipping clutch when their car is sluggish or hesitates.
Often, the initial symptom will surface as a driveability complaint. Like any other driveability issue, it’s important to ask the right questions that will help the tech analyze the complaint. This is also why it’s so important to road-test the vehicle and confirm the complaint before the diagnostic process begins. By doing so, you will prevent doing the service and then having to call the customer after a road test to tell him or her that a clutch replacement is needed to fix the problem.
Detecting clutch slippage on a road test shouldn’t be a problem. Look for high pedal engagement that will indicate a thin disc. Borderline cases will show up as the clutch engages after a shift, or when the driver attempts to accelerate uphill while the engine is in its torque band.
Another common complaint will be that the clutch doesn’t disengage. Most Mazdas use a hydraulic system to operate the clutch. Diagnosing this system should present little challenge to even a less-experienced technician. If the fluid is low, it had to go somewhere. Check the bellhousing-mounted slave cylinder for leaks as well as the master cylinder on the firewall. Don’t forget to look under the dash, where the master cylinder pushrod comes through to connect to the pedal, for signs of fluid leakage.
Another cause of poor disengagement that won’t be as easy to detect is a loose piece of clutch disc or cushioning spring getting jammed between the pressure plate and the disc. Usually a result of hard engagement, it’s possible to pull a piece of the clutch disc material off the disc or to fracture the springs in the disc that are there to cushion the engagement. These pieces can find their way between the disc and surface of the pressure plate, and they will take up the free space normally created when the clutch is depressed.
Although not as common, it’s possible for a seized pilot bearing to lock the transmission input shaft to the crankshaft, preventing clutch disengagement. The tip-off that you are dealing with a mechanical rather than a hydraulic problem will be evident in the feel of the clutch pedal. If presented with a soft, mushy pedal, suspect that air has entered the system as a result of the fluid level getting low. If you have a nice, strong pedal and no disengagement, it’s a safe bet that there is a mechanical problem.
Then there are the noises. Grinding or growling will be the most common sounds you’ll hear. If the noise occurs when the pedal is depressed, there is a problem with the throw-out or pilot bearing. If the noise is evident when the clutch is released, transmission bearings will have to be replaced.
Oftentimes, the customer will be skeptical and you’ll need to provide some educational details. Explain to him or her that when the clutch pedal is depressed, the transmission is no longer connected to the engine. It has stopped spinning and that’s why the noise is gone. Of course, if the car has enough miles on it that the transmission bearings are worn, it’s a good idea to suggest that the clutch be inspected and replaced, if needed, while the transmission is removed for service. It’s also a good time to remind your customer that the transmission oil should be replaced as part of their routine maintenance schedule.
The actual nuts and bolts of clutch replacement are straightforward and will present little challenge to most technicians. When performing clutch service on a FWD vehicle like the Protege, you’ll find yourself working with many components on the front end of the car. This creates an ideal starting point for entry-level techs, as it gives them experience in many aspects of undercar service, as well as teaches them the organizational skills necessary to perform a big job.
Rather than list the steps required to do the job (your service information will have that), we’ll touch on some of the tips that will help you make this job successful.
Of course, the first concern is safety whenever you’re preparing to remove heavy components, like the transaxle, from a vehicle. Be sure it’s positioned on the lift correctly and don’t forget to remove the negative battery cable. In many cases, the battery will be removed for access. Once the car is on the lift, and you’re looking over the job deciding what has to be removed, grab a can of penetrating oil and give the hardware you’ll be dealing with a shot. Most of this hardware hasn’t been touched since the vehicle was built and a little penetrating oil will go a long way to make them easier to deal with.
As you prepare to remove the wheels, take a few minutes and check the condition of the steering components. If the car needs ball joints, tie rod service or sway bar links, now is the time to make note. The same goes for brake and axle components, as well as the transmission’s side seals. You’re already under the car, so it’s a good opportunity to save your customer some money and, at the same time, it’s certainly a good situation for you.
On front-wheel-drive cars, whether you’re removing the transmission or changing a timing belt, the need will arise to remove the motor mounts and/or crossmembers. An engine support is a good investment. This simple device does a good job of supporting the engine, while being unobtrusive, and eliminates the need for single pole or jack stands.
Mazda, like most other car makers, uses captured bolts for mounting crossmembers. Take care not to break them. In the case of the Protege, these bolts are splined to hold them in place. If one breaks, it’s possible to knock it out and fish in a new one, but it’s certainly not easy and will cost you more time than it would to heat and remove the nut. Once the transmission and clutch assembly are removed, closely inspect the flywheel. The best course is to have every flywheel refaced, but depending on your situation, it may not always be possible. However, if the clutch surface shows signs of excessive heat, hot spots, surface cracking or warpage, the flywheel will have to be refaced to ensure smooth clutch engagement.
If you don’t think the surface needs to be refaced, clean it with a surface conditioning disc and solvent. If you are in doubt, have it resurfaced. It’s expensive to have to pull the job down a second time to have the wheel refaced in order to eliminate the clutch chatter that occurs when putting a new clutch against a bad surface.
While you’re inspecting the flywheel, don’t overlook the ring gear. Mazdas aren’t known to have a problem with the gears, but if there’s damage to the teeth, you’ll be doing the customer a favor by recommending that it be replaced now. This is also the time to look closely at the rear main seal and core plugs that are accessible only with the transmission removed.
The advent of replacement clutch kits was a huge step forward in ensuring that all the necessary parts get replaced during clutch service. With the pilot bearing, release bearing, pressure plate and disc all packaged together, it makes it very convenient (plus the alignment tool is a nice touch). There are a lot of tricks out there for removing pilot bearings, but few are as effective as the tool designed for the job. If you find yourself faced with a bearing that has come apart, and only the outer race remains in the crankshaft, we’ve had good luck cutting the race with a die grinder to remove it. When installing the clutch cover, tighten the cover bolts evenly, so as not to damage the clutch cover. Be careful not to overtighten the bolts. Using a torque wrench isn’t a bad idea.
Turning our attention to the transaxle, clean out the bell housing and remove the clutch throw-out fork and release bearing. When reassembling the parts, be sure to lubricate all the points that move, particularly where there is metal-to-metal contact the fork pivot, as well as the forks where the release bearing sits. You should also lube the transmission snout on which the bearing rides, as well as the input shaft. Be stingy with the grease, since it doesn’t take much to do the job and we don’t want an excessive amount finding its way to the disc.
Our final step in preparing the transaxle to be reinstalled is to clean and lubricate the dowel holes so it will slide right up to the engine. Reinstall the removed parts, fill the transaxle with fresh oil, change and flush the clutch fluid and you’re ready for the road test.
Anyone who’s seen a “zoom-zoom” Mazda TV commercial knows the automaker believes that a performance image will sell its products. So we shouldn’t be surprised if we have Mazda owners asking to upgrade their clutch when a replacement is required. From a labor standpoint, it changes nothing to install a high-performance clutch package. Most enthusiasts will be looking for a clutch package that has a higher coefficient of friction than the stock disc, as well as a stronger pressure plate.
The discs are available with variety of hub designs, and all have stronger take-up springs that will better withstand the anticipated hard driving style. The most aggressive discs will have a solid hub with no springs. These are best reserved for only the most serious racers; the average enthusiast will find them much too harsh for everyday driving, not to mention the additional stress they put on the driveline.
The same cautions have to be taken with lightweight, aluminum flywheels. It may sound like a good idea in the enthusiast magazines to lighten up the rotating mass for a vehicle that will see track use. But the average owner won’t be happy with the change for everyday driving. Without the inertia of a heavy flywheel, it takes a deft touch to get the car moving without stalling or having to slip the clutch neither will make the everyday vehicle driver happy.
The bottom line is that, as technicians, we should find clutch jobs to be both profitable and rewarding, with plenty of opportunities for necessary, additional repairs that will save our customers money on labor and boost our bottom line.