Neil
Supporter
Bob Putnam has the correct answer. On Ford muscle cars a "Long" style pressure plate was used with centrifugal counterweights on their release levers. As RPM increases, the counterweights centrifugal force increases as the square of RPM, increasing the clamping pressure on the clutch disc. It was not uncommon at high RPM for the clutch pedal to not be able to overcome the effect of the counterweights. At lower RPM the clutch would operate normally and the transmission would shift OK.
Check to see if you have a Long-style pressure plate with centrifugal weights. Some designs had removable weights; if so, try replacing the weights with lighter ones or remove them altogether. A diaphram-type pressure plate would probably be a better choice these days.
Check to see if you have a Long-style pressure plate with centrifugal weights. Some designs had removable weights; if so, try replacing the weights with lighter ones or remove them altogether. A diaphram-type pressure plate would probably be a better choice these days.