• 2019

Grasping the Clutch

Repairing and Replacing a Legend’s Clutch

In the 21st century, automotive technology continues to change. While new devices are brought into the vehicle, others pass into history. One of those fading technologies is the manual transmission.

The rule used to be that if you had a performance vehicle, a 4-speed manual gearbox was required to draw the most performance out of the engine. That’s no longer true. The new electronically controlled, multi-speed transmissions convert power as efficiently as the manual units in years past. And they shift faster, too!

However, there are still times when the burning desire (and the need) to shift manually hits. Thankfully, one vehicle still offers a manual transmission. The Jeep® Wrangler. The one drawback of this throwback, though, is the vehicle’s clutch. Clutches still wear out and have to be replaced. How often that occurs and how often it is required depends on how the vehicle is driven.

Clutch Testing and Diagnosis

Before we review the clutch replacement procedures, it’s important to test and diagnose clutch problems. Drive the vehicle at normal speeds and shift through all the gear ranges. Observe the clutch action. If the clutch chatters, grabs, slips or does not release properly, inspect the clutch components. If the problem is just noise or hard shifting, it might not be the clutch. Further diagnosis of the transmission or another driveline component can reveal the source of the problem.

Fluid contamination is a common cause of clutch malfunctions, as well. Oil, water or clutch fluid on the clutch disc and pressure plate surfaces will cause chatter, slip and grab. Oil contamination indicates a leak at either the rear main seal or transmission input shaft. Clutch fluid leaks usually come from damaged slave cylinder push rod seals. Heat build-up caused by slippage between the pressure plate, disc and flywheel can bake oil residue onto these parts. Look for residue colors ranging from amber to black.

Road splash contamination is caused by dirt and water entering the clutch housing due to loose bolts and housing cracks. Driving through deep-water puddles when taking a Jeep® Wrangler off road can force water into the housing through such openings.

Clutch Removal and Inspection

Our subject vehicle for this article is a 2014 Jeep Wrangler equipped with the popular Pentastar® 3.6L V6 engine. Position the Jeep Wrangler on a hoist and shift the transmission into Neutral. Slide the shift lever boot up and remove the shift lever bolt and lever. Next, raise the vehicle and remove the skid plates. Remove the drain plug and drain the fluid from the transmission. Remove the catalyst assembly.

Mark the transmission flange and driveshaft for installation reference before removing the driveshaft. Note the two marks shown in Figure 1. If the vehicle is 4×4 equipped, mark the transfer case before removing the driveshaft. If equipped, remove the transfer case linkage, wiring connectors and vent hoses. Then, remove the transfer case.

Pull the hydraulic line clip, line from the bracket, the bracket mounting bolts and the bracket from the slave cylinder. Remove the slave cylinder by pulling it straight back. Do not allow the release lever plunger to pivot more than 2º in either direction in the cylinder slave bore. Fluid leakage can result.

Next, remove the backup lamp switch wiring connector, then the starter. Support the transmission with a jack, then remove the crossmember. Slide it out the left side. Remove the transmission mount. Then, remove the shift tower and cover the opening with a clean rag. Finally, remove the transmission bolts from the engine, move the transmission rearward and remove it from under the vehicle.

Loosen the pressure plate bolts evenly and in rotation to relieve spring tension and to avoid warping the clutch plate. Remove the pressure plate bolts, the pressure plate and the clutch disc.

Before installation of the new clutch disc, inspect the flywheel. Look for heat damage (discoloration), scratches and scoring on the surface. Flywheel machining is not recommended. The surface is machined to a unique contour and machining will negate this feature. Minor scoring can be cleaned up with 180-grit emery cloth. Do not remove more than 0.003″ of stock. If scoring is excessive, replace the flywheel.

Also, check the runout on the flywheel. Measure it with a dial indicator. It should not exceed 0.003″ at a spot 1/4″ from the outer edge. If runout is excessive, replace the flywheel.

Figure 1

Installing the New Clutch

Before installing the new clutch, lightly scuff the flywheel face with 180-grit emery cloth, then clean it with a wax and grease remover. Lubricate the pilot bearing with high-temperature bearing grease. Next, check the runout and operation of the new clutch disc. It should slide freely on the transmission input shaft splines.

With the disc on the input shaft, check the face runout with a dial indicator. Check the runout at the disc hub 1/4″ from the outer edge of the facing. Runout should not exceed 0.020″. If it does, purchase a new clutch disc.

Figure 2

Position the clutch disc on the flywheel with the side marked flywheel against the flywheel. If not marked, the fl at side of the disc hub goes toward the flywheel. Refer to Figure 2. Insert the clutch alignment tool (3) through the clutch disc and into the pilot bearing. Position the pressure plate (2) over the disc and on the flywheel (1).

Install the pressure plate bolts finger tight. Use only the factory bolts to mount the pressure plate. NOTE: The bolts must be the correct size! Tighten the pressure plate bolts evenly and in rotation a few threads at a time. The bolts must be tightened evenly and to the correct torque to prevent distortion of the pressure plate.

To finish the installation, apply a light coat of high-temperature bearing grease to the clutch disc hub and the splines of the transmission input shaft. Do not over-lubricate the splines. Grease contamination of the clutch disc can result.

Installing the Transmission

To finish the clutch replacement project, re-install the transmission in the vehicle. Installation is straightforward and the reverse of the removal procedures. Without getting into specifics, here are some important points.

First, apply a light coat of high-temperature grease to the contact surfaces of the following components: (1) release forkball stud, (2) release bearing slide surface, (3) input shaft splines, (4) release bearing bore, (5) propeller shaft slip yoke and (6) pilot bearing.

Next, check the alignment of the clutch before installing the transmission. After the transmission is installed and the slave cylinder is back in place, bleed the hydraulic system. Don’t forget to properly align the transmission flange and driveshaft with the marks made during removal (see Figure 1). Finally, fill the transmission with the proper lubricant.