Apache,
If you have noticed on a clutch plate there is some springs that go around the hub. These are buffer springs and when the flywheel and pressure plate grab the clutch disc, the springs take the snap out of the take-off. When these springs over-heat or get a lot of use, they become week and cause your problem, so you will need a new clutch disc and while you are in there, replace the pressure plate and release bearing and check the flywheel for cracks, Be sure to lube the pilot bearing before assembly.
Truck Tinker
