When my HJ was having that problem, the clutch was completely dry inside. Gordie informed me of the same method and I tried it but as he mentioned, that only works if glazing is your problem. I ended up replacing the clutch disk, the pressure plate and having the flywheel resurfaced at a machine shop. I don't know which of these fixed it but it's great now. With the J when you dig into it that deep and the problem isn't obvious (and it may not be on your car) it's best to just replace it all when you have it apart. Of course, that costs money even if you do the work yourself. My car shook so bad when you let the clutch out the whole rear end just seemed to bounce. It works like new today.