Before you or your mechanic rip out your clutch you may want
to review this article, gaining insight and maybe saving future problems. All too
often the installer places the car on the rack and starts to pull out the transmission
without asking:
• Why did this clutch fail?
• Is the failure due to normal wear and tare, or did something else cause this problem?
This is the most important step in repairing the vehicle. The best indication that
this clutch system might have failed for unusual reasons is the mileage. From the
1950’s through the 1970’s, 50,000 to 60,000 miles of usage was considered a good
life span for a clutch. However, with improvements in technology, clutch systems
are lasting a lot longer these days. It is quite common for a clutch system to last
more than 80,000 miles. It all depends on the driver, the usage of the vehicle and
the maintenance of the system.
With today’s improvements in clutch systems, you should be suspicious of a clutch
system that failed before 35,000 miles. You should search for reasons other than
normal wear and tear. If you can’t detect the cause of failure the first time, you
will be dealing with it again.
Some clutch failures are not caused by a component of the clutch system, so just
removing and replacing clutch components will not solve the problem of premature
failure. It is quite possible that this is a problem the you or the mechanic cannot
fix. In some cases, fixing the problem means changing your driving habits. In others,
it might mean that you should buy a larger truck to tow that fifth-wheel trailer.
Unless you can identify the cause of the failure. It is in your best interest to
determine what caused this clutch system to fail. Acting too quickly to remove the
components from the vehicle can eliminate some clues as to what really happened.
Taking time for a few simple diagnostic steps can enhance your ability to determine
why this clutch failed.
If your vehicle is drivable, take it for a test drive. Try to re-experience the details
and symptoms of the problem. Knowing exactly what the symptoms are will allow you
to focus on the probable cause and will save you a great deal of time The most-common
clutch-system complaints are:
• No release- preventing shifting.
• Slipping
• Clutch chatters or shudders
• Noise
• The vehicle will not move.
Most of these common clutch-system failures can be broken down into the following
categories as to causes:
• Normal system wear or failure
• Driver or system abuse
• Installation failures
• Lack of maintenance
• Manufacturing defects.
In speculating as to what might have caused the failure, here is a general guideline
as it relates to the mileage. Obviously there are exceptions, but as a rule of thumb,
manufacturing defects or installation problems usually occur immediately or shortly
after the installation of a new clutch kit. Problems caused by lack of maintenance
and abuse usually show up in the mid-life of the clutch system- anywhere from 20,000
to 35,000 miles. Failures from normal wear and tear generally occur after more than
50,000 miles.
Asking yourself the following questions might shed some light on what caused the
failure:
• Is that the original clutch or has it been replaced?
If it has been replaced, who did the work? Chances are the clutch was installed incorrectly.
• Has the vehicle been taken in to have the clutch adjusted? Some cable-operated
and some hydraulic systems are self-adjusting, but several are not. If the vehicle
requires adjustment, were you aware of that?
• If the vehicle is a truck or is equipped with a trailer hitch, what is it hauling
or towing? You may need a heavy-duty replacement clutch system.
Also, and important issue is who is driving the vehicle. Let’s face it; we all in
our youth liked to break those tires loose every once in a while, is there a teenager
in the picture, does your wife ride the clutch at stop lights?
Some of these questions may seem a little delicate, but if one of these problems
is the reason the clutch system failed, you will be fixing the vehicle over again
and again. It’s best to identify these types of problems early, before the repair.
Next step is to examine the vehicle itself. Is there any collision damage? If there
is, it is possible that the frame is damaged, and this could misalign the engine
and transmission, causing release problems. A broken transmission mount or engine
mount also could misalign the drivetrain. If any of these conditions exist, they
need to be repaired before you replace the clutch or else you will experience the
same problems.
Examining the underside of the drivetrain for oil leaks, especially around the bottom
of the bellhousing. If oil is present, it could be that the rear main seal off the
engine or the front seal of the transmission needs to be replaced. Oil contamination
of the clutch disc will cause slippage and eventually burn up the facing.
Next check the clutch-release system. If the vehicle has a mechanical or cable release
system, check for free play at the clutch fork. The failure may have been caused
by an incorrect adjustment. If the free-play adjustment was insufficient, the cover
diaphragm or levers began to rise toward the bearing as the facing of the clutch
disc began to wear. If the bearing was in continuous contact with the diaphragm,
the clutch cover became partially engaged and allowed the clutch disc to slip, thus
burning up the disc. If the problem is non-release on a vehicle with a cable system
and the cable cannot be adjusted further, replace the cable. Clutch cables stretch
and need to be inspected with every clutch replacement.
If the vehicle has a hydraulic clutch system, check for hydraulic leaks at the slave
cylinder or the master cylinder. If either or both are leaking, they should be replaced.
If the problems is non-release, replacing these components could correct the problem.
If the problem is noise coming from the clutch system, a simple test can identify
the source of the noise before you tear into the system. There are two potential
bearing-noise makers in the clutch system-the release bearing and the pilot bearing.
To determine which one, if either, is making the noise follow these steps:
Step 1 With the engine running and the transmission in neutral, if the noise
occurs it is in the transmission, most likely the front bearing supporting the input
shaft.
Step 2 If that is not the problem, place your foot on the clutch pedal and begin to depress the pedal. If you begin to hear the noise at this point, the problem is the clutch release bearing. If not, proceed to the next step.
Step 3 Push the clutch pedal all the way to the
floor. If you hear the noise at this point it is the pilot bearing or bushing.
If you do not hear any noise during this test, the problem is not in the clutch
system. Identifying these conditions early before removing and replacing the
components goes a long way toward preventing a recurrence of the problem.
As you remove the clutch components from the vehicle, look for wear on components
you normally don’t replace, like the clutch fork and ball stud. If they are
worn, replace them. Inspect the quill, or front-bearing retainer sleeve, of
the transmission for wear. If it is worn, replace it. If the quill is part of
the from transmission case and cannot be removed as in some models of the Ford
Escort, Taurus, and Tempo and the Mercury Topaz, repair kits are available.
And most important, when you re-install the clutch, install a complete matched
set clutch kit when purchasing clutch kit be sure to ask for and get warranty.
Warranties are available up to 12 months on standard kits and even out to 24
months with high performance clutch assemblies. Also another overlooked or thought
not to be worth it is the resurface the flywheel do not skip this critical step.
A few simple steps before you tear it down can save you time, effort and profits
in the long run- not to mention a very happy clutch system when you can identify
the cause of the clutch system’s premature failure and prevent it from happening
again.
This is a reprint of an article from Transmission Magazine. You may want to
subscribe to this very informative magazine if you are into automotive repair.
Clutch Main Page
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