tech

Clutches, Linkages & Bellhousings for Jeep Conversions

The Novak Guide to
Clutches, Linkages & Bellhousings for Jeep® Conversions
Article provided by Novak Conversions - experts in Jeep conversions since 1967

This article contains the culmination of decades of experience setting up clutch systems for Jeep conversion applications. We will first identify the components involved, and then introduce the science of setting up a proper clutch release system.

Flywheel
The flywheel provides a friction surface for the clutch disc, a torque buffering mass, a mounting surface for the pressure plate, a mounting for the starter driven gear, and on some engines the flywheel is a factor in engine balance.

The condition of the friction surface of the flywheel is important for proper clutch function. The surface should be smooth and free of burned spots and surface cracks. Used flywheels can be resurfaced. This should be done by grinding rather than lathe turning as less material is removed. The amount of material removed from the face can affect which clutch release bearing should be used. A flywheel should always be checked for runout on the engine it will be used on. Face runout should not exceed .005" of an inch.

Pressure Plate
This is the other half of the driving friction surface. It mounts on the flywheel. It consists of four main parts and is more correctly called a clutch cover assembly. These parts are the pressure plate itself, the springs (or spring, if a diaphragm type), the clutch cover, and the release arms. There are two basic designs of clutches usually referred to by the spring type.

These are the Rockford™ (diaphragm spring type) and the Borg and Beck™ (coil spring type). The coil spring type is also called a three-finger type, referring to the three release arms this style requires to compress the coil springs.

The "softest" clutch is the diaphragm type. It also requires the least amount of travel to release. The diaphragm type clutch works good in lightweight, low geared vehicles. It is not the best clutch for high RPM use as the diaphragm spring will stay "flat" or released from the centrifugal force generated by the RPM. A variation of the diaphragm type was used for a while by GM, that to some extent helped this problem. This was called the Hi-Cone diaphragm type and was designed so the spring - instead of being flat when released - still had a slight bevel. These Hi-Cone units were not bad but still won't hold like the Borg and Beck coil spring type. Aftermarket units like the Centerforce®, use centrifugal weights to counteract this high-rpm flattening and subsequent loosening. It should be noted that this is not typically a concern of the Jeep enthusiast as high RPM horsepower is not as much an interest as low-RPM torque. It should be pointed out that the spring itself is the "release arms" of a diaphragm type clutch. Note that when interchanging from one type to the other, you will require a different throwout bearing. The three-finger style requires a longer throwout vs. the diaphram type, which uses a shorter throwout bearing. More on this later...

The fourth part of the pressure plate assembly is the cover. The pressure plate, spring (or springs) and release arms are attached to the cover in such a manner that, when the release bearing pushes on the three arms or the diaphragm spring, it causes a leveraged action to take place. This counteracts the spring pressure and lifts the pressure plate off the clutch disc, releasing the clutch.

As stated above, the diaphragm type clutch takes slightly less travel to release and requires about .030 total air gap when released. The coil spring type requires about .040 to .050 total air gap when released. Air gap is the clearance between the clutch disc, flywheel, and pressure plate with the clutch released. A total air gap of .050 will measure .025 between each side of the disc.

Clutch Disc
This is the "driven" part of the clutch. It has a friction material riveted to each side of a wavy spring (called a marcel). This is attached to a splined hub that the transmission input gear protrudes into.

There are basically two common types of friction material used for clutch lining. These are organic and metallic. The organic is best for all around use. The metallic is preferred by some for severe duty applications but requires high spring pressures and is hard on the flywheel and pressure plate friction surfaces. Avoid solid hub clutches and clutches without marcel as they will always chatter when used in vehicles with a rear differential mounted on springs (as opposed to a transaxle design).

Pilot Bushing
In most cases, this is a porous bronze, pre-lubed bushing rather than an actual bearing, as it is often called. A few applications still use an actual bearing and others use a needle roller type bearing, but by far, the most common type is bronze. You cannot use a roller bearing on a transmission shaft originally designed for a bronze bushing due to different type of heat treatment on the shafts.

For a list of several versions of pilot bushings offered by Novak, jump here.

The pilot bushing is seldom thought of as a part of the clutch system but it is one of the most vital parts of the system. It pilots the end of the transmission input gear in the crankshaft. If it is worn or not running "true", it can cause serious clutch problems or transmission failure. Pilot bushing bore runout should always be checked with a dial indicator and should be within .002 total. The bronze bushing type should be a press fit in the crankshaft bore. It must be installed carefully. It should have between .002 and .003 clearance on the transmission shaft when installed. The pilot bushing is only functional when the clutch is disengaged but it is a factor in input gear alignment at ALL times.

Clutch alignment is critical to installation. Otherwise, expect the transmission to not line up with the pilot bushing.

It is always a good idea to use an input gear (of the proper diameter) or clutch aligning tool when installing the clutch on any engine. With the clutch disc aligned on the pilot bushing it becomes a simple matter when installing the transmission to engage the splines and bolt up the transmission . If this simple procedure is not done, the transmission shaft won't line up and the temptation will be great to "pull it up with the bolts" which damages the front transmission bearing, pilot bushing, and more than likely will break an ear off the transmission or adapter. The transmission should slip in freely to mate up with the face of the bellhousing.

Clutch Release Bearing
As its name implies, this is the bearing that releases the clutch. It is often referred to as a "throw-out" bearing. They come on a number of different style carriers. The carriers, in some cases, vary considerably with the particular engine. In the GM line, for example, the bearings are all the same but there are several different carriers that vary about 1/2" between the shortest and longest. Which to use usually depends on the style of pressure plate being used, but substituting one length for another can often be used to the installer's great advantage. AMC, Ford & Mopar and others are far less generous with the variety of lengths available. This will be covered in more detail later in this article.

Because the release bearing only works when the clutch is being released it usually lasts quite a long time. However, improper linkage adjustment or riding the clutch with your foot when driving can wear the bearing prematurely. Normally there should be a minimum of 1/16" clearance between the face of the bearing and the three release fingers or diaphragm spring of the pressure plate when the clutch is engaged. This fact is important and will be discussed further when we get to the part about setting up the clutch linkage.

Clutch Release Fork
This is the arm or lever that the linkage operates that moves the release bearing. There are several different styles of release arm. The most common in automotive use is the fork type that pivots on a rocker. This type requires a rearward force to move the release bearing forward. Note now that the following is key to your understanding of the clutch system: The ratio of the arm is the difference in length between the pivot point and the release bearing centerline divided by the length from the pivot point to where the linkage attaches. The ratio of the fork is important and will be used in the linkage setup section later in this article.

GM, Ford, and AMC all use a pivot type release arm as their most common type. Some late GM, Pinto, Jeep and a few others use a non-rocker arm. This style pivots on the passenger side of center and is direct acting. That is, it takes a forward movement of the linkage to move the release bearing forward. This is not as suitable as the rocker system as it usually complicates the linkage requirements.

Regarding GM clutch forks, there are two basic types of manufacture used for the pivot type forks. These are stamped steel and forged steel. The stamped steel type uses a flat steel retainer spring that is riveted to the fork. These forks must be used with mushroom-head type pivots. The forged steel forks must use the ball-head type pivot. (This is different than the ball-on-pedestal AMC type.) These forged forks are retained on the pivot by a spring-wire retainer that fits in a groove machined in the ball pocket in the fork.

Release Arm Pivot
As its name implies, this is the support that the release arm pivots on. There are basically two types. One pivots on a ball-ended stud that screws into the bellhousing. The other type is an actual bearing ball that sits in a pedestal type socket that is part of the bellhousing. GM, Ford, and early AMC use the screw-in type. Late AMC favors the ball type.

There is an adjustable length pivot (shown) with an adjustment range of 1-3/8 to 1-1/2 inches available for GM engines that can sometimes be used to compensate for variations in flywheel, clutch disc, and release bearing thickness. More about this in the troubleshooting section.

Both ball and mushroom-head GM pivots are available in 1-3/8 and 1-1/2" length (overall length when not [this is important] installed in the bellhousing). It is very important to use the correct style of pivot in relation to the type of arm being used.

Transmission Front Bearing Retainer
This great device has three critical functions. This first is as its name implies. The second is to provide a register on which the bellhousing must center. This is feature is sometimes overlooked with expensive consequences. Thirdly, its tubular snout is the surface on which the throwout bearing rides on its way in to depress the springs of the pressure plate. Conversions often require special and modified retainers to acheive compatibility.

Bellhousing
This provides a mounting place for the transmission, as well as a means of aligning the transmission to the engine. In some applications it also has a structural mounting function.

The alignment function is extremely important. Unfortunately, this is the most often overlooked and least understood part about the bellhousing.

Most people who have worked on these parts realize there are aligning pins in the engine block that register with holes in the bellhousing. What they do not realize is, there can be a variation in the location of these holes and this variation can affect clutch and transmission life. How to check bellhousing alignment will be covered in its own section further on in this article.

Clutch Linkage
This consists of everything between your foot and the clutch release arm. The linkags is the method of transferring the force of your left foot into the bellhousing and pressure plate release. The linkage can be mechanical, cable type or hydraulic. Note here that problems tend to show up because there are usually several choices of release arms and bearings for any particular family of engines. Choosing the wrong parts can get the linkage out of relationship and cause problems that can only be solved by removing the parts and starting over with other parts. The linkage cannot be made to compensate incorrect choice of release bearing or fork.

Cable Style Linkage
Cable linkages may seem appealing because it is easy to understand and simple to hook up. However, once past this, the installer may discover that it has high friction, stretches, sticks, rusts, freezes, frays and breaks. A cable type clutch should probably be the last choice of the three types of linkages.

Cable linkages work fine in smaller applications such as motorbikes and light cars, but they have an unsustainable record in light and heavy truck applications.

Some CJ & Commando Jeeps from 1972-1974 used a cable release, with subpar results as evidenced by the duration of their implementation.

Mechanical Style Linkage
Next is the mechanical linkage which is, with a few exceptions, the type found on the majority of Jeeps® built prior to 1987.

There are several basic styles of Jeep mechanical linkage but all are used in nearly their original configuration when doing an engine conversion. They usually consists of a pushrod at the pedal, a bellcrank and an additional pushrod actuating the fork. Earlier systems use pullrods, bellcranks and cables in lieu of pushrods, effectively reversing the way the systems works.

The mechanical linkage is largely a successful method of clutch release. One drawback obvious to many off-roaders is the tendency of some of these to bind during frame and powertrain flex and differentiation.

Hydraulic Style Linkage
Hydraulic clutch linkage systems have moved into dominance in the past two decades, and generally with good reason.

The most common rendition of this linkage consists of the pedal pushrod against a master piston / cylinder, a high-pressure tube or line and a slave piston / cylinder whose pushrod pushes the clutch release arm.

A less common style of hydraulic release is the internal hydraulic release bearing. This design combines the piston and bearing into one unit, eliminating the pivot, fork (or release arm) and separate throwout bearing.

A Jeep internal hydraulic throwout bearing, common in YJ Wranglers and XJ Cherokees between 1987-1994. They are innovative in design but have gained notoriety for leak failures. Hardened o-rings are usually the culprit, and this occurs as much from non-use (drying out) as overuse (abrasion wear). To add serious insult to significant injury is to have the failure prone Peugeot transmission (1987-1988) with a bad internal release bearing.

A word is in order at this point about hydraulic clutches and the misconceptions that surround them. Many individuals believe that it is the interaction of the hydraulic master and slave cylinders through which the force against the clutch pressure plate is multiplied. In fact, the actual multiplication of force occurs in two different areas of the clutch system. First it is in the leverage of the clutch pedal assembly. The master cylinder actuator being closer to the fulcrum of the pedal arm, distance is reduced and force is increased, through that great principle of physics with which all mechanically minded individuals are aware. Secondly, additional force is created through the leverage of the clutch release arm. In basic principle, this is the way clutches have been virtually since the inception of the automobile.

The hydraulic system, therefore, is simply a method of transferring that leverage - or better said, of transmitting force through the incompressable hydraulic fluid. This is very similar in principle as a good old mechanical linkage via pushrods, bellcranks or cables. Essentially no multiplication of force occurs within the hydraulic circuit itself as is common with other hydraulic systems like jacks, rams and presses.

This is an aftermarket internal hydraulic throwout bearing. The drawback is the expense, at over $300

This leads to the next useful principle: Nearly every clutch master cylinder is matched for size to its connected slave cylinder for a largely 1-to-1 relationship. So, a 3/4" bore master cylinder should connect to a 3/4" slave cylinder. A 1" master should have a 1" slave cylinder. A master cylinder that is larger will yield a rather spectacularly blown out slave cylinder and a master cylinder that is smaller will yield a rather disappointing lack of travel for your left foot's efforts. There are occasions where this ratio can vary slightly from this, but rarely more than 15%.

Once the installer understands this, the rest will come together more easily and in accordance with the principles outlined for conventional mechanical clutch systems.

Hydraulic systems can be simple, but mostly when there are existing provisions for mounting the master and/or slave cylinders. Thin firewalls and bellhousings without proper structural provisions for slave cylinders are the chief entanglements that hamper retrofit.

Shown is Novak's hydraulic slave cylinder retrofit system for Chevy bellhousings. This makes excellent use of YJ & TJ Wrangler master cylinders. Click here for more information...

Sequence of Linkage Setup
Let's assume we are using a Chevrolet engine, Rockford clutch (diaphragm type), and the back of the block is "bare" but the crankshaft is in the block.

Install the pilot bushing to be used for the particular engine-transmission combination in the crankshaft. Then, with a suitable dial indicator, check the bore of the pilot bushing. Runout should not exceed .002 (two thousandths) of an inch.

Temporarily install the bellhousing to be used on the block it will be used with. (This is important as the results of this test can vary with a different block or bellhousing.) Test the bellhousing for "runout" on both its bore and face as described in the trouble-shooting section. Bore runout must be within .007" and face runout to within .004". If you don't, can't, or won't check bellhousing alignment, do not be surprised if you have problems. These will not show up right away. It may be several thousand miles before a clutch hub, pilot bushing, or transmission fails.

Temporarily bolt the transmission to the bellhousing. Look through the release fork opening to determine that the pilot area is at least 3/8" engaged into the pilot bushing bore. If it is not, the pilot bushing is incorrect and a longer bushing must be installed, or in some cases, the bushing can be installed at less than full depth.

Remove the transmission and bellhousing. Install the flywheel on the engine. Most engines use grade 8 (high-strength) bolts with a special low profile head to clear the disc hub. Do not substitute regular bolts for these special bolts.

Check the face of the flywheel for runout with a dial indicator. Runout should not exceed .005". If it does, the flywheel should be resurfaced. If runout exists after resurfacing, the fault is either in the resurfacing job or there are burrs, dirt, or dings on the crankshaft or flywheel hub. Remember there is end play in the crankshaft bearings and this must be held in one direction when checking flywheel runout (or bellhousing face runout).

Install the clutch disc and pressure plate on the flywheel. Use a clutch aligning tool or the transmission itself. This is important as it will simplify transmission installation and prevent assembly damage. Tighten the mounting bolts 1/4 turn at a time so as not to distort the clutch cover.

Choosing a Release Arm
Stay alert on this step. Things get kind of involved but it is very important. The release arm must be the same ratio as the arm that was originally in the Jeep for the linkage to work. Notice we said ratio, not length. Assume the release arm is the typical rocker type with its pivot between the release bearing and the linkage attach point and figure the ratio as follows.

Measure the Jeep arm from the pivot point to the center of the clutch release bearing. Also, measure the distance from the pivot point to where the linkage attaches. Divide the inner length into the outer length to obtain the ratio of the arm. (Example: A stock Jeep arm from a 1976 CJ5 measures 3.1" from the pivot in and 6.2" from the pivot out to where the linkage pushes. Divide the 3.1" into 6.2" and you find this arm has a 2-to-1 ratio. This means if you move the end of the arm 1", the release bearing would have to move 1/2" in the opposite direction.)

Now assume we need a Chevy arm to work with this same linkage. Chevy arms all measure 3" from the pivot in. We need a 2-to-1 ratio (as this is what the Jeep linkage and many GM pressure plates are designed for) on the Chevy arm so we require a Chevy arm 6" long from the pivot out. Unfortunately no such Chevy arm exists. The shortest non-hydraulic arm is 6.5" from the pivot out. Some are as much as 9" pivot out. The short arm is 2.17 to 1 and the long arm is 3 to 1. The long arm must be shortened 3" to be compatible with the linkage. What about the short arm? You could make it work on this particular vehicle by sacrificing some free play (at the release bearing) as well as air gap at the disc (full release condition). This particular short Chevy arm also has an end shape that is correct for the Jeep linkage we used as an example. This 6½" long Chevy arm is available from Novak as our #RAGM.

All of this changes when a vehicle with different style original linkage is being worked on.

The early style CJ's (pre-1971 with 4 cylinder) for example, had a very short release arm; the remaining leverage occurs additionally in the linkage system. However, if this arm is measured from the pivot in and divided into the pivot out length it will be found to have a ratio of 2.4" to 1. As previously stated, there is no factory GM release arm with the required outer length that has the proper type end. A longer arm can be shortened and the end modified to accept the Jeep linkage. However, Novak has these arms available as our #RAV6.

From all this, it should be observed that the release arm to be used with a conversion will sometimes have to be modified to get the proper ratio and this must be done at the start of the installation. Trying to use an arm that is too long will result in problems that cannot be corrected with changes in linkage.

GM Clutch Release Bearings
The following procedure should help you to determine which of the six different length clutch release bearings you will need to properly operate the clutch.

Let's assume we are still working with a 10½" or 11" Rockford (diaphragm type) clutch on a GM engine. Other makes of engine, Ford or Jeep for example, or a Borg and Beck (3 finger type clutch) procedure would be same with exceptions that we will mention later.

Install the flywheel (always have it resurfaced before this procedure), clutch disc, pressure plate and clutch housing on the engine. Be advised that there can be NO oil or grease on your hands, the flywheel or pressure plate friction surfaces, or on the clutch disc. If there is, the clutch will grab (chatter) when being engaged.

Install the correct length clutch fork on a 1½" long pivot that has the correct head type for the retainer on the fork (refer to fork and pivot information previously discussed). Position the fork so it sticks out of the clutch housing at about 4 or 5 degrees less than a right angle with the engine centerline (this would be when looking down on the engine from above—the fork should be ahead of, or less than a 90 degree angle by 4 or 5 degrees). Hold the fork at this angle and measure from the inner front thrust surfaces of the fork to the diaphragm spring (or fingers) of the clutch. Choose a release bearing length from the "A" dimension in the chart below that is closest to the measured length.

When measuring, try to keep the inner ends of the fork parallel with the clutch—it is possible to be off as much as 3/16" if not parallel.

Obtain a release bearing based on the above measurement and install it on the fork. Be advised that forks with the flat type spring require that the tips of the fork AS WELL AS THE TIPS OF THE SPRING are installed in the groove of the release bearing.

-A- Length -B- Overall Length Part Number 3/4" 1-17/64" N 4068 15/16" 1-5/8" N 1741 1" 1-41/64" N 2001 1-1/16" 1-11/16" N 1466 1-1/4" 1-7/8" N 1086

This chart shows the length of the bearing in inches. Most auto parts stores only stock a couple of these release bearings and they may not be the best ones for your swap. This chart lists five bearings by the critical "A" measurement; groove to face dimension as referred to in this article.

Install the transmission on the clutch housing. The release bearing must be able to move away from the diaphragm spring approximately 1/16 to 1/8" (this is the "free play"). At this point you should be able to move the release bearing back and forward with the fork. The bearing, when against the clutch, should leave the release fork positioned at 4 or 5 degrees LESS than a right angle with the engine centerline and allow it to be moved away from the clutch 1/16 to 1/8". If this condition does not exists, do not install the assembly into the Jeep until it does. If not, you may need a different clutch release bearing or pivot or you may have the wrong fork.

As stated earlier in this article, if you are switching from a three-finger type to a diaphram style pressure plate, you will require a shorter throwout bearing. The inverse is, of course, true if you are going the other way.

The bearing must clear the clutch or it will turn all the time and will wear out quickly—also the clutch may slip as it may be partially released.

At this point (finally) the engine and transmission are ready for installation and hookup of linkage. Install the remaining bellhousing and transmission bolts if these parts do not have to be removed again.

The engine, transmission, and transfer case should now be installed in the Jeep. With the engine mounted, the connection of the clutch linkage can proceed.

As previously stated, when mechanical linkage was used originally on a vehicle, we advise staying with the same.

Regardless of whether the stock linkage pushed or pulled, it must do so in as straight a line as possible. This will keep friction to a minimum.On installations where the engine must be moved (such as pre-1971 CJ's) the clutch bracket that supports the frame end of the bellcrank must be relocated. This must be to a location that will put the bellcrank at a right angle to the engine and level from side to side (parallel to the ground).

On 1972-86 CJ's where a bracket must be made to support the Jeep clutch cross-shaft, the cross-shaft must end up at a right angle to the engine in both the vertical and horizontal planes.

The arms on either style bellcrank must be positioned for maximum mechanical advantage. This means they cannot angle more than about 35 to 40 degrees from either side of a right angle to the push (or pull) rod that they connect to. This alignment angle is established at the bellcrank and the operating rods are then modified to whatever length is required to keep the bellcrank or cross-shaft at this position with the release bearing at least 1/16" off the three release arms of the pressure plate.

Have a helper push the clutch pedal to the floorboard and hold it there. Check the air gap between the flywheel and the clutch disc with a feeler gage. As stated previously, it should be .030" for a diaphragm clutch and .040 to .050 for a coil spring clutch.

Release and adjust the linkage until the air gap is correct for the type of clutch being used.

Check for at least 1/16" clearance between the clutch release arms (or diaphragm spring) and the release bearing. If the bearing face contacts the clutch with the clutch in the engaged position (not enough free play) you will have to go to the next shorter length release bearing to obtain the required air gap and free play.

Bellhousing Alignment
On any engine using a standard shift transmission, with or without an adapter, it is important to check the bellhousing locating bore location relative to the crankshaft. The potential for transmission failure or premature wear is so great, due to misalignment at this point, that no engine should be assembled without being checked. The checking procedure is quite simple. Correcting misalignment is not so simple but must be done to insure normal service from the transmission. A dial indicator is required, as well as a suitable means to mount this instrument on the engine crankshaft.

A dial indicator (right) is a device that has an arm or contact point, suitably connected to a pointer, that moves in front of a dial with markings on its face. These markings usually represent .001" each. The purpose of a dial indicator is to measure in thousandths of an inch that can be read directly on the dial of the indicator.

To check a bellhousing, mount it on the engine it's going to be used with, make sure there are no burrs or dirt on the block or bellhousing. All bellhousing to block bolts should be in and tight. Mount the dial indicator on the crankshaft of the engine using a suitable magnetic base attachment or mechanical clamping means. The contact point of the indicator should be touching the bore of the bellhousing. The indicator must be mounted rigidly enough so it does not move on its mounting to prevent false readings. Rotate the engine by hand with the spark plugs removed and observe the reading on the dial. Keep adjusting the dial assembly until the needle moves the least amount per rotation. When you have acheived the least amount of needle movement throught he 360 degree sweep of the indicator, this is your runout. You can then determine the direction it is offset by the movement of the needle.

The total number of thousandths misalignment of the bore relative to the crankshaft is read directly on the dial. Total runout should not exceed .007", with .010" being maximum. The greater the misalignment, the sooner transmission problems and failure will occur. A symptom of misalignment is unusual wear of the pilot bushing. We have checked stock Chevy bellhousings on engines that were out more than 1/32" (.032"). Some Ford one are reportedly worse. Anything over .010" runout must be corrected before the engine and bellhousing are put in service or you can count on pilot bushing, transmission, and clutch problems, followed by transmission failure. The simplest way to correct misalignment is to try another bellhousing or bellhousings. Machining the bellhousing is the best cure but offset dowel pins are simpler. Shims between the block and bellhousing will also work if you have the patience to use this method. Offset dowel pins are sometimes available from "speed shops."

For Reference
The pressure plate must move about .100 to .120 of an inch to RELEASE THE DISC and provide .030 to .050 air gap between the disc and the flywheel.

• A 9" clutch has about a 4.5-to-1 arm or diaphragm ratio.
• A 10.5" clutch has about a 6-to-1 arm or diaphragm ratio.
• An 11" clutch has about a 6.6-to-1 arm or diaphragm ratio.

The release bearing must move away from the fingers or diaphragm sping at least 1/16"
(.0625 rounded off to .06) for freeplay.

The release fork ratio is determined as described in the release fork section.

Example: A 10.5" clutch and a #RAGM GM release arm (2.17 ratio).

So, 0.120" required movement multiplied by the ratio of a 10.5" clutch equals .72" plus .06" movement of release bearing for freeplay equals .78 of an inch. Multiply .78" by the ratio of the release fork (2.17") equals 1.69" (or 1-11/16") of travel required where the linkage attaches. It doesn't matter if the linkage is mechanical, cable, or hydraulic, it must be able to move the end of this arm with this pressure plate the above indicated amount in order to properly release the clutch disc.

For comparison, using the same release arm with a 9" clutch only requires about 1-5/16" movement while the 11" clutch requires almost 1-7/8" of movement -- nearly 9/16" more. It is the ratio of the pressure plate that makes this difference. This is also exactly why the hydraulic slave system on 1980 to 1986 4 cylinder CJ's will not completely release a 10.5" or 11" clutch on a conversion engine. It does not have the necessary travel. In this particular Jeep both the operating and slave cylinders would have to be changed to get more travel.

However, if the slave system is engineered correctly with the proper ratios, full release can be attained with 10.5" clutches. See the Novak #HCR3 kit.

Symptom:
Clutch drags. It won't release completely and the transmission grinds when shifted

Symptom:
Clutch Slippage

Symptom:
Clutch chatters when engaging

Symptom:
Pedal pulsates when pushed to floor (3-finger coil spring type only)

Symptom:
Pedal pulsates at start of release

Symptom:
Noise; clicking or rattling at idle RPM with the pedal released

Symptom:
Noise; whirring or grinding when clutch is released (pedal depressed)

Symptom:
Noise; chattering or "buzzing" when clutch is released

Symptom:
Pedal is hard to push and hold down

A cutaway view of a clutch assembly, three finger type. Image courtesy of McLeod Industries.

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