How to Be a Clutch Hitter - Transmission Digest

How to Be a Clutch Hitter

The clutch-driven vehicle will be here for the foreseeable future. The good news is that driver skills have declined, which makes clutch replacement a bigger share of your business.

How to Be a Clutch Hitter

Up To Standards

Subject: Installation of manual-transmission clutches
Essential Reading: Shop Owner, Center Manager, Diagnostician, R & R
Author: Mike Weinberg, Rockland Standard Gear, Contributing Editor

Up To Standards

  • Subject: Installation of manual-transmission clutches
  • Essential Reading: Shop Owner, Center Manager, Diagnostician, R&R
  • Author: Mike Weinberg, Rockland Standard Gear, Contributing Editor

Manual-transmission availability in late-model cars has been declining steadily as automatic transmissions have become the manufacturers’ favorite option. This is a byproduct of several issues.

The first is that the federal government, through the EPA and other agencies, doesn’t like sticks. The automatic transmission shifts at open throttle; the manual trans shifts at closed throttle. The automatic makes controlling emissions a lot simpler, as the driver has little control.

The second issue is production volume. The automatic usually is manufactured by either the carmaker (Ford, Chrysler or GM) or, in the case of imports, Aisin, ZF etc. In either event the huge volume of production provides economy of scale, bringing costs down considerably. This means that most domestic vehicles with manual transmissions are either sport models or work vehicles; the proportion of import vehicles with manual transmissions is larger, as the rest of the world still knows how to drive a stick shift. This will change as the newer models begin to be equipped with dual-clutch models shifted by computer without a clutch pedal. This design gets rid of the torque converter and reduces the weight borne by the crankshaft.

The clutch-driven vehicle will be here for the foreseeable future. The good news is that driver skills have declined, which makes clutch replacement a bigger share of your business.

Clutch inspection

Every time you remove a manual transmission for repair, it makes good technical sense and good business practice to remove the clutch for inspection. A large percentage of manual-transmission failure and damage is created by clutch slippage or release problems. The few extra minutes you spend removing the clutch for inspection will be offset by the larger number of clutches you sell and the drop in comebacks on manual-transmission repairs.

Another often-overlooked item is the flywheel and hydraulic or cable system that applies and releases the clutch. Many vehicles today are equipped with dual-mass flywheels, which always need to be inspected. A dual-mass flywheel has primary and secondary plates. The inner plate, which mates with the clutch disc, is spring loaded to help absorb harmonic vibrations resulting from the engine’s firing pulses. The flywheel is precisely matched to the damper mechanism on the clutch disc to filter out the engine harmonics to create a smooth clutch engagement and eliminate gear rattle and neutral-rollover noise in the transmission.

It is very important to move the inner plate against the outer plate on the dual-mass flywheel and note the amount of travel. Excessive travel and low turning resistance indicate a spring failure or wear on the dual mass and the need for replacement. Most of the major manufacturers supply a solid-steel flywheel and matching clutch set to replace a dual-mass setup, lowering the cost of repairs. The clutch disc has a much-increased damper section to compensate for the solid flywheel and must be used as a matched set.

Other components that need to be inspected carefully include the hydraulic release system, which consists of master and slave cylinders, clutch cables, fork, release (throw-out) bearing, fork pivot ball, and pilot bushing or bearing. A worn pivot ball or clutch fork will create all kinds of noise when the clutch is released and occasional noise or clicking when the clutch is engaged. The pilot bushing or bearing aligns the input shaft into the centerline of the crank. If the bushing has excessive wear the input shaft will have increased runout, which usually shows up in 4th-gear jump-out.

Most of the pilot bushings are made of oilite bronze material. The bronze is heated during manufacture and placed in oil. As it cools, the bronze absorbs the oil. Never lubricate a bronze bushing. To do so will cause the bushing to carbonize the lube and create a birdlike noise when the clutch pedal is depressed, or the input shaft will seize to the bushing and cause transmission damage, as the input will not stop turning during the clutch release. This beats the synchronizers to death in short order, as they are designed to slow the gears or speed them up to synchronize the shift but do not have the capacity to fight the engine torque. Pilot bearings should always be lubricated so that the rollers can turn freely with minimal friction.

Transmission inspection

Doing a first-class clutch job is really simple if you follow the rules. When the transmission is removed inspect the input splines for rust, straightness, and burrs or dings. Any missed items here will prevent proper movement of the disc on the input and poor clutch release or engagement. Pay attention to the quill tube, or input-bearing retainer, upon which the release bearing rides. Any wear or damage here will create release and engagement problems. On certain transmissions the quill tube is part of the case and not replaceable separately. In some instances repair kits are available to sleeve the tube, and it may be possible to cut the tube to a smaller diameter and add your own sleeve, restoring it to the correct internal bore for the release bearing. Most newer transmissions have the quill tube as part of the hydraulic slave cylinder, so this is no longer an issue.

If the ring gear is good on the flywheel, always resurface the flywheel on a grinder. Never use a brake lathe for this, as the hot spots on the flywheel will cause the lathe bit to skip and you will not get a good finish. The flywheel must be either resurfaced to be flat and concentric and parallel to the crank flange, or replaced.

Another quick thing to check is endplay on the crank. Do this with a pry bar on the crank flange to make sure the thrust bearing on the engine is good and the crank has no endplay. Be very careful in handling a clutch disc. Do not get your fingers on the friction material. The oil from your fingertips is enough to take some life off the disc. Handle the disc by holding the outside edges or the damper assembly. Always slide the disc onto the input shaft to assure free movement along the splines and to make sure the splines match. LIGHTLY lubricate the splines with some Neverseize to prevent rust and aid the movement of the disc. Lightly means just a little, as too much will be thrown off by centrifugal force and wind up on the disc.

Make sure that there are no oil leaks on the transmission input or front case. Oil is the instant killer of clutch friction material and a rapid failure that the manufacturer will not warrant. Always use an input shaft or clutch-alignment tool when installing the pressure plate. Tighten the pressure-plate bolts in a star pattern a few turns at a time to draw the pressure plate down on the flywheel. Failure to do so will bend the pressure plate. This is not a place for air guns. When the bolts are fully tightened the fingers of the diaphragm should be level and parallel to the flywheel.

Installation precautions

Use a jack when installing the transmission into the disc splines and pilot bearing. Never hang a unit on the disc, as you will bend the Marcel plate and have a crooked disc that will never release properly. Make sure the alignment dowels are in the engine block and are in good condition. A light sanding and some light lube will make the bellhousing easier to draw down flush to the block.

Misalignment problems create some hard-to-solve issues and a lot of wasted time. Look at the old disc you are replacing. If it is covered with a fine red dust, this unit has an alignment problem. Don’t ask me where the red dust comes from, but take it to the bank that if the clutch has a fine red dust on it the unit was misaligned.

Make sure no wires or clips get trapped between the bell and the block. If you have an alignment issue you will need to mount a dial indicator on the crank flange and check runout on the bellhousing, where the trans comes through. This is difficult or impossible on many front-wheel-drive units or transmissions that have an integral bellhousing, but you need to make sure that the trans is aligned properly.

Carefully adjust the clutch cable or fully bleed the hydraulics. On the hydraulics the best way to do this is with a vacuum bleeder hooked up to the slave-cylinder bleed plug. A number of designs are very hard to bleed because of positioning of the master cylinder. A good rule of thumb is to check under the hood and see whether the master cylinder is parallel to the floor. If it is not, jack up one end of the vehicle to make it so, and the bleed process will go quickly. Remember that 3 or 4 inches of clutch travel at the pedal will result in about 0.050 inch of movement at the disc.

Advanced clutch diagnostics

Some people can just swap parts and never be curious as how the originals failed; others need to know and learn. By looking carefully at the components that came off the vehicle you can tell a lot about how and why they failed.

The disc material may be burnt, glazed or oil soaked. The disc’s Marcel cushion plate may be bent or flat; it should have a wave in it to cushion application. Damper springs can be loose, broken or missing. Examine the damper-assembly stop pins for wear or damage. These pins limit the travel of the damper. If they are worn or bent the damper is over-traveling. This is caused by someone who likes to side-step the clutch at high rpm or downshift from 5th to 2nd without applying the brakes.

See figures 1-4 for problems and causes. After you have completed your repairs, take the customer on a test drive and let them drive. In some instances it will open your eyes. Some gentle instruction may be the difference between a good customer relationship and a comeback to be argued over. Remember, the driver controls the life of the clutch. Most older drivers will not be a problem; look out for the 18-year-old who is impressing his girlfriend.

You May Also Like

Learn New Things

You are not supposed to get to the finish line in pristine condition. You are supposed to cross the line a burnt out, beat up hulk, and through the smoke and leakage, yell, “WHAT A RIDE!”

Up To Standards

Author: Mike WeinbergSubject Matter: What a ride!Issue: Technician shortage

You are not supposed to get to the finish line in pristine condition. You are supposed to cross the line a burnt out, beat up hulk, and through the smoke and leakage, yell, “WHAT A RIDE!”

MP3023 T-Case: Simple Mechanics, Complex Electronics

The MP3023 is an active automatic transfer case that is found in a wide variety of vehicles. This unit will be found in GM trucks 2007-13, Jeep Grand Cherokees 2011-19, and in Dodge Durangos 2010-up. We will be discussing the Jeep version here, which has very sophisticated control electronics. The transfer cases are basically all the same across the product line, but there are considerable variations in the electronics, which will make diagnostics outside of the transfer case a learning experience.

Simple Routines Can Leat To Solutions

For whatever reason, the tech lines get an inordinate number of calls regarding a few specific is-sues. That such a high volume of calls is generated by just a few problems leads to the belief that we need to revisit and speak about the lack of understanding by the tech-nician that leads to all this wasted time and phone traffic, as well as failure to get the job right the first time. Let’s start out the year by get-ting to the nitty-gritty of why cer-tain issues seem to confuse so many people.

Lubricants: Understanding the Mysteries

Lubricating oils or lubricants have been around since the invention of the wheel, and every class or type of machinery uses and needs them. But, how much do we really understand about these products and about the amazing amount of engineering that is found in a can?

Tires Vastly Improved, but Check the Specs

The advancement of technology in the automotive field is rapid and unrelenting. Forces that shape the marketplace, state and federal regulations, the need to attract new customers, and the need to be different and at the same time profitable are driving the car makers to develop technology at a pace never seen before.

Other Posts

Are We Speaking the Same Language?

If you are repairing transmissions for a living, you will invariably spend some time on the phone ordering parts and speaking with technical hotlines to assist in your diagnosis of problems. Having been on both ends of a tech line for over half a century and an equal amount of time buying parts, I have learned a whole new language. To be successful communicating with those entities, one must understand the language and be speaking about the same correct topic with whoever is on the other end of the conversation.

Electronics In Dual Clutch Units

This article is the final segment of our exploration of the dual-clutch transmission, or direct shift gear box (VW and Audi) or DualTronic in BorgWarner’s brand. We have included several schematics from a VW Touran model, as VW has the largest amount of these transmissions in use. VW using its VAS 5051 diagnostic system provides for, as they say, “guided fault finding,” which means that a test schedule is available for the unit and provides testing for sensors, actuators and the mechatronic (computerized) valve body.

Hydraulic & Fluid Controls in Dual-Clutch Units

To recap, we have looked at how the dual-clutch transmission functions, essentially two gear boxes in one with the input shafts driven by hydraulically applied clutch packs that drive three concentric shafts that are one inside the other. The innermost shaft drives a gerotor-type of fluid pump that provides pressurized fluid to actuate the dual clutches, lubricate and cool the components, and shift the transmission into the selected gear. The next two shafts are driven by the two clutch packs with one shaft shifting the even-number gears and one shifting the odd-numbered gears.

Controls Make Shifts Happen in Milliseconds

If you have been following the previous chapters of this series of articles, you are starting to understand the function of dual-clutch transmissions. We have used illustrations from the VW Direct Shift Gear Box (DSG) as VW has about 2 million of these units on the road at present.