Tips for Installation & Eliminating Problems
us your suggestions, comments, and tips.
Throwout Bearing Installation
One of the most common mistakes made on GM vehicles - mostly pickups - is the
improper installation of the throwout bearing onto the clutch fork. The spring
(in black) on the clutch fork (in red) should be placed in the gap between the
rear flange on the bearing and the front flange. You should not be able to see
spring on the back of the bearing. Symptoms of an improperly installed bearing
are poor release, a mushy feeling pedal, short clutch life, and not being able
to adjust for correct free play on mechanical linkage systems. This bearing and
fork spring combination has been used from the late 1960's up to the present.
A worn pilot bushing
can cause chatter, poor release, and can loosen the hub clutch disk. If the center
hub of your old disk is loose, be sure to change your pilot bearing. Installing
a new pilot bushing or bearing sounds simple. Removing the old one can be difficult.
One of the old tricks is to fill the bearing with grease and then drive an alignment
tool into the bearing, letting the grease push it out. This usually messy, but
it normally works - unless you have a bushing that is worn. If the hole in the
bushing is much larger than the alignment tool, you get a face full of grease
when you try to knock it out. Another trick is to find a bolt that you can thread
into the bushing - you may have to tap some threads into it. Screw the bolt into
the bushing. When it hits the bottom keep screwing it in and the bushing will
be pulled out by the bolt. Some applications use a needle bearing. These can be
difficult to remove. Try the bolt trick on these too. If you prefer a bearing
instead of a bushing, some earlier Ford's and Chevy's can accept the needle bearings
that are used on the later engines.
from a 11" clutch to 12"
Almost all 11" GM clutches can be replaced with a 12" clutch & pressure plate.
I don't know of any that can't be changed, but I'm sure that someone will find
one; so, I'll say almost all can be changed. To do this you MUST surface the flywheel.
There are two basic styles of pressure plates - lever type & diaphragm type.
The lever type has a lever height of 2 inches, while the diaphragm type can have
several different heights, depending on the application. The earlier styles had
a flat diaphragm and used the tall throwout bearing. The later models used a raised
diaphragm and the short bearing. If you replace the 11" flat diaphragm pressure
plate with a 12", you must use the short bearing. The 12" will have a lever height
of 2" whether it is a lever type or diaphragm type. You can also have choice of
strength with the 12" pressure plates. The 12" used in the 454 cid applications
can installed in place of the 350 cid unit. Just tell your clutch shop that you
want a CA1908 instead of a CA1909 and he will know you want a heavy duty version.
Flywheels are one of the parts of a clutch job that are very often overlooked.
The flywheel is exposed to just as much heat as the pressure plate. It can and
does warp just as much as the pressure plate. It deserves just as much TLC as
the pressure plate and clutch. Check it for hot spots (discolored areas), warpage,
and scoring. While you are doing this, look at the ring gear. If the teeth look
worn, now is the time to replace the gear. It is a usually an inexpensive item.
Change it if it looks worn.
Some flywheels (mostly imports) cannot be surfaced very much at all. They have
such a short throwout bearing travel that grinding the flywheel might move the
pressure plate toward the engine far enough that the clutch may not release properly.
Chevy's have a problem when the flywheel has been surfaced too much. The flywheel
bolts hit the springs in the clutch disk. This is easy to check with the flywheel
off. Put a bolt and lockwasher in the hole, lay the disk in place and look through
back of the flywheel to see how much clearance you have. Some Ford's also have
a common problem. Some aftermarket disks have some small rivets that will rub
on the flywheel's inner diameter just inside the wear surface. This is easily
fixed. If you don't have access to another brand disk, while your flywheel is
being surfaced, have a small recess cut on the inner diameter. About 1/8" is usually
enough. If the rivets rub the flywheel, you will get a poor release and possibly
& Beck Lever Style Pressure Plate
The lever type pressure plate is almost a thing of the past in Chevy's. It was
used on almost all GM trucks from the 50's to the early 80's. The same basic design
has been used on vehicles from the 30's to the present in everything from fork
lifts to farm tractors. It is still a very common unit in the industry. Many suppliers
now replace this unit with the diaphragm pressure plate. The lever style will
tolerate much more heat and abuse than the diaphragm style; but, it is more expensive
to build, so we now see more of the diaphragm units in the older trucks that were
originally equipped with the lever style. The lever style can usually be rebuilt
several times, while the diaphragm type is normally a boat anchor by the time
it needs to be replaced.
If you are working on a lever type unit, there is one thing to to keep in mind.
When the unit is bolted to the flywheel, the levers will move toward the engine
about 1/2". This is normal. As the clutch wears, the levers will move toward the
rear. This will reduce the free play at the bearing and is the reason you have
to adjust the clutch periodically. DO NOT reach in and lift the levers or allow
the transmission shaft to drag on them. If this happens, a small strut under the
rear of lever can fall out of position. It can be put back in place fairly easily
with a small mirror and a piece of wire. If this happens, it is usually the lever
at the 6 o'clock position that has the problem. The struts on the levers at the
top cannot fall out of position.
the Bearing Retainer
throwout bearing retainer, which is bolted to the front of the transmission,
is an item that is usually ignored and very often worn out. It should be smooth
and be free of any low spots. Ford's and Chevy's are both prone to having problems
here. Many Ford's were originally equipped with an aluminum retainer, and is frequently
found to be galled. Aftermarket suppliers usually have cast iron retainers. Get
one of these if you can. Chevy's are all cast iron. Some Ford front wheel drive
cars have the aluminum retainer made into the transmission. If you find one of
these worn, you don't have to replace the transmission case. There is a repair
sleeve with a special bearing available. The ID is larger than in the OE bearing.
Be aware of this. You might find one that has been repaired, and the original
size bearing will not fit the retainer. The bearing should slide back and forth
easily without any binding. Do not put a coating of grease on it. You can put
a small amount on it and then wipe it off, leaving only a light film of grease.
A worn retainer can cause a high pedal effort, clutch chatter, and poor release.
While you're looking in this area, check to see if there is any transmission grease
around the inside of the retainer. If you see any grease here, remove the retainer
and replace the seal inside the retainer. Reinstall with a new gasket. Do not
use a gasket compound in place of the gasket, because it also acts as a spacer.
Put some thread sealer on the retainer bolts to prevent transmission grease form
migrating through the threads and contaminating the disk.
Fork and Ball
There are several things to check on the fork. Make sure the spring on the back
is not broken. Some early GM forks did not have springs. The springs showed up
in the mid 1970's. The spring not only holds the fork to the ball, but holds the
bearing back toward the fork so it does not rattle around. The ball should
snap solidly in place in it's socket. The spring should hold it in place and should
not try to slip off the shoulder of the ball. The socket should be smooth and
not worn. Put a small dab of grease in the socket. If the socket is worn, you
will usually hear a popping sound when the pedal is pushed. S10 pickups have a
common problem of a squeaking sound. This usually occurs when the clutch is not
depressed, but can sometimes be heard with the pedal pushed in. This is caused
by a dry pivot ball. It is not serious and will not cause any damage, but can
be very annoying. There is a bulletin that shows how to make the ball greasable
from the outside. It's worthwhile doing this if you already have the bellhousing
off. Ford's use several different systems that hold the fork on. One common problem
with Ford's is the type that uses a small "L" shaped bracket as the pivot. This
bracket is bad about working loose in the bellhousing. A replacement repair kit
is available from Ford.
Turbo Diesel Dual Mass Flywheel
When GM introduced the 6.5 l. turbo diesel engine, a new type flywheel was used.
It was called dual mass. The flywheel consists of a separate plate for the friction
surface and another unit bolted to the crankshaft. The two units spin in unison,
with the torque transmitted through thin friction surfaces internal to the flywheel.
Belleville spring washers keep a preload on the friction surfaces. Some large
springs on the outer diameter of the flywheel absorb the shock load of the engine
that would normally be transmitted to the transmission. The purpose of the flywheel
is to save the transmission. With all this stuff inside the flywheel, it's easy
to see that there is a much greater chance of problems occurring in this area
- and it does! When the clutch and pressure plate has to be changed in one of
these trucks, the flywheel usually must be replaced. The main plate surface is
steel and is normally severely warped. These plates can very seldom be resurfaced.
A replacement conventional flywheel and clutch set with a special dampner yoke
has been introduced for this unit, but it has been even less successful than the
original. Under heavy duty use, the disks have a tendency to mechanically fail.
Even though the dual mass unit is much more expensive, it will normally be more
cost effective in the long run. GM. has dropped the dual mass unit, but it is
still available through clutch shops.
When Ford introduced the hydraulic clutch master cylinder in 1984 in their pickups,
a rash of clutch release problems starting showing up. The area where the master
cylinder is bolted to the firewall is prone to flexing when the clutch is depressed.
This can get so severe that it will crack the firewall. If the firewall moves
when the clutch is depressed, the volume of fluid to the slave cylinder is decreased
which reduces the travel of the throw-out bearing, which will not allow the clutch
to release completely. The only repair for this condition is to reinforce the
firewall area. A brace for this is available from Ford dealerships. This is a
sheet metal part which must be screwed in place. Another style brace is available
from many clutch shops. It is made of steel plate and does not require any drilling.
It simply mounts behind the master cylinder.
to Master Cylinder Link
A poor release on a Ford F series pickup with a hydraulic clutch can often be
caused by a small
link connected to the end of the clutch and brake pedal pivot shaft. This
is the link that pushes in the master cylinder rod. The link is simply pressed
onto the end of the knurled pedal shaft. Over time, this link will work loose
on the knurls and will fail to push the rod into the master cylinder far enough
to release the clutch. To check for
this condition, remove the pushrod locking clip and slip the rod off the link.
Raise the clutch pedal to the top of its travel and try to replace the rod over
the link pin. If the pedal must be lowered in order to replace the rod, the link
has slipped and must be replaced. Do not try to simply tighten the mounting nut.
It will not work. The link must be replaced.
Throw-Out Bearing Retainer
The bearing retainer on many Fords is made of
aluminum. These retainers are bad about galling, making the pedal
hard to push. This will not only make your leg tired, but will also
damage the pedal linkage. They can gaull to the point of actually breaking
the pedal. The retainer must be smooth and free of nicks and scratches.
If it is not too bad, it can be polished with emory cloth. If it will
not clean up, replace it. Many clutch shops have replacement retainers
made of cast iron. Use one of these if you can find one. They are not
as bad about gaulling and will last much longer. Be sure to use a new
gasket on the retainer and some oil resistant thread sealer on the bolts.
Put a very light film of grease on the retainer and then wipe it off.
The new throw-out bearing should have enough lube in its grease groove
when you buy it. If not, put a small amount in the groove before you install
Some of the cable operated Fords have an automatic adjuster mounted on the clutch
pedal. It has plastic teeth that can wear which will not allow the clutch to release
completely. If you have one of these cars with a clutch that will not release,
check to see if the pedal has excessive free play. If you can lift the pedal to
the top of its travel and it will not stay, or will not move the cable whin depressed,
then you might have a bad adjuster. There are metal replacements available.
Style Pressure Plate
For several years, Ford used a pressure plate manufactured by Long in many of
their vehicles from Mustangs to F series pickups. This pressure plate has 3 levers
instead of a diaphram. The main problem with these units is that they have a tendency
to chatter. A diaphram style pressure plate is available for these units. The
covers are stiffer and the levers are eliminated. These replacement pressure plates
are usually much smoother. If you can find one of these, use it rather than the
When Ford introduceed the 7.3 diesel with a ZF 5 speed transmission in 1987, a
special flywheel was used on this engine. It is called a dual mass flywheel. The
clutch used with this flywheel is 11" diameter. The same size clutch is used on
the F250 and F350. It is not suprising that an 11" clutch in a 1 ton truck has
a short life if it is used much at all. A 6 cylinder 1/2 ton pickup used an 11"
clutch with almost the same clamp load. If you are changing out a dual mass flywheel
on a truck that will see heavy use, you might consider one of the upgrades designed
for your particular truck. The 11" 1988 thru 1994 F250, F350, and F450 7.3 non-turbo
flywheel can be replaced by a special 11 7/8" flywheel designed for this retrofit..
This will allow you to use the 11 7/8" clutch and pressure plate designed for
this flywheel. The 1993 and 1994 7.3 turbo diesels were equipped with the 11 7/8"
clutch but used different flywheels.
The ZF 5 speed transmission in the F250 thru F450 Ford diesel trucks is very sensitive
to the resonance that produced by the engine. In order to protect the transmission,
dual mass flywheel was developed. The flywheel has springs and friction surfaces
in it instead of in the clutch disk. This relocates the dampner form the disk
to the flywheel. The springs and rubber bumpers separate the main part of the
flywheel, which is bolted to the crankshaft, from the secondary part of the flywheel
where the clutch and pressure plate is mounted. Two friction surfaces inside the
flywheel act as torque limiters to absorb any torque peakes that might damage
the transmission. At the present time, Valeo is the only manufacturer of thes
When replacing the Ford dual mass flywheels, always use new bolts. These are available
from Ford. New bolts are important because they have a special thread sealant
on them. If the old bolts are reused it is possible that engine oil can leak through
the threads and contaminate the new clutch.