Clutch problem diagnosis and repair
Clutch problem diagnosis and repairs may be required whether you have a hydraulic or a manually operated clutch assembly. Clutches are made of friction material that is designed to wear away similar to the way brake pads wear. The longevity of the clutch disc itself actually relies on the skill of the drivers operating the vehicle. A driver that hovers their foot on the clutch pedal allowing the disc to slip against the flywheel will find that their clutch disc needs to be replaced more often. Replacing the clutch disc is not the only type of maintenance that is required when it comes to manual transmissions. Vehicles with external clutch linkage will require periodic lubrication of these components. Failure to perform lubricating operations can also reduce the life of your disc and cause other clutch problems.
Slipping clutch problemsThe clutch slipping condition is probably the most common issue complained about from drivers with manual transmissions. Clutch slippage is a condition in which the engine overpowers the friction coupling attaching it to the transmission and in turn the drive wheels.There are several ways of checking for a slipping clutch. Many vehicles with a manual transmission will have Tach or RPM indicator. When driving the vehicle you can select a higher gear and apply some heavy acceleration and watch your rpm's compared to vehicle speed. If the RPMs swing up high and the speed does not increase or increases slowly this is a sign of a slipping clutch problem. When you have proper clutch operation RPMs and speed increases smoothly at about the same rate.
The parking brake should be applied and all four wheels should be blocked to prevent the vehicle from surging forward. In a clutch stall test the clutch should be able to be released and stall the engine. Note that the causes of a slipping clutch problem can be caused by other vehicle related problems. An example would be a rear main seal oil leak that is dripping on the clutch disc itself. An oil soaked clutch will definitely slip just as a worn clutch disc. This happened on my 300zx and I wrote an article about the other clutch problem the Z had. A worn-out pressure plate can also fail to positively engage the disc against the flywheel. This is why I recommend that when a worn clutch disc is replaced that you use a complete clutch kit. Most clutch kits contain a pressure plate, throw out bearing, pilot pushing and a clutch disc.
Clutch dragging and bindingAlthough a clutch dragging and binding is not as common as a slipping clutch condition mentioned above I have seen it enough to briefly discuss it. If the clutch disc is not completely released when the clutch petal is fully depressed this would be considered a dragging or binding clutch.When the clutch petal is pushed all the way to the floor the clutch should fully release and allow the manual transmission input shaft to stop turning. If the shaft continues to turn all of the functions such as shifting can become difficult.
Continue to hold the clutch pedal against the floor. Then shift the transmission into the neutral position. Wait for about 5 seconds and then attempt to put the transmission into reverse. If there is a lot of gear clash noise or it is difficult to get the transmission into reverse this could be a sign that the main shaft is still spinning. Your mechanic can raise the vehicle on a lift and with the clutch pedal completely engaged or pushed to the floor he can see if the wheels are still turning.
Clutch Kits
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The other way to test for a slipping clutch problem is to perform a stall test. This is best performed by an experienced mechanic that has done this before. When performing a stall test safety should be a concern. 
