Clutch slip??

[Glenn W]

92 sho 5sp, My son says the clutch is slipping off and on,I have driven the car 5 different times and the clutch is fine, he says he can be going down the road and all of a sudden the revs shoot up for a sec than it seems to fix itself. I haev given it the dive test and all seems well,What could it be??

 

[sdpatt]

You may want to ask him where he is resting his left foot while he is driving.