Manual transmission maintenance

By Steve Temple,

Is your manual transmission getting harder to shift? Does it feel like it just doesn't grab like it used to, or maybe it's starting to chatter or vibrate? Is your clutch slipping? A worn clutch may be the culprit here, or it could be the result of something else, such as a transmission misalignment. One obvious sign that misalignment is the problem would be rust residue on the disc and pressure plate.

Pinpoint the problem

In the case of this driveline, one of the two transmission dowel pins was missing, which allowed the transmission to tilt down on the passenger side of the vehicle, causing the misalignment. The input shaft on the transmission was also heavily worn where it rides on the pilot bearing, due to the misalignment.

Correcting the cause of the problem was simply a matter of making a new dowel pin for the transmission and installing it. Although this relatively simple fix is just one example of many possible problems that might need to be addressed, the procedure for service and reassembly applies to clutches in general.

Make adjustments

Prior to putting the clutch back together, it is always recommended to resurface the flywheel and install a new pilot bearing. You should also apply a drop of adhesive to the threads of the bolts prior to bolting the flywheel to the engine.
manual transmission clutch being cleaned
Then, clean the flywheel and pressure plate with acetone to ensure an oil-free surface (this is one area where you don't want any lubrication at all). Make sure to use the correct alignment tool when placing the disc up to the flywheel. Once again, before bolting and torqueing the pressure plate to the flywheel, apply a drop of adhesive to the threads of the bolts.

Inspect for wear

In addition to replacing the pilot bearing, follow the same procedure for the throwout bearing on the transmission, as release issues can be caused due to a worn pilot bearing and/or scoring of the inside collar of the throwout bearing. Always inspect hardware for wear and replace with new, factory-specified or high-quality aftermarket hardware.

Check your manual

Before beginning any clutch removal and installation procedure, it's a good idea to start by checking your factory-approved service manual. Use only factory-recommended fluids in transmission and clutch release hydraulic systems to ensure proper release and maximum life of the clutch components. Also, be sure to check the bellhousing and/or engine block dowel pins for wear. Using all proper dowel pins helps ensure proper bellhousing alignment, including parallelism and concentricity.

Clutch assembly

Remember to always resurface the flywheel prior to installing a new clutch disc and pressure plate assembly. This ensures the clutch disc friction material seats into the flywheel properly for maximum holding capacity and service life. Also, check the flywheel for runout prior to and following the resurfacing process. If excessive runout is found, check the flywheel for proper balance.

Finger pointing to a manual transmission clutch

Examine the clutch disc on the transmission input shaft before installing onto the flywheel to ensure fitment. It's a good idea to scrutinize your vehicle for prior clutch problems.

Often, clutch chatter, vibrations and premature wear are not related to the clutch disc and pressure plate. Problems such as misalignment, flywheel resurfacing, pedal/freeplay adjustment and runout are responsible for the majority of clutch failures, premature wear and poor performance. By following the tips mentioned above, though, you can keep your vehicle's clutch out of spin city.