I can definatly see it when I have the clutch cover off and use the clutch.
I had it in gear and rocked it back and forth a gazzilion times to see if it would slip. no such luck. Then I pulled the lever in and let it out. Did that I do not know how many times, and then it finally did it. the pressure plate would not mesh back in again. Just hit the inner hub and stayed ontop of it.
Thats when the slipping happens obviuosly, because the pressure plate can not press against the outer friction disk as hard as it should.
I am now wondering if maybe the dog gear on the inner hub nut may not be working properly and maybe cause the pressure plate to get off-set ever so slightly and that is causing the teeth to get out of alignment??
I always torque the pressure plate bolts to 8# as that is what is required. I have never had one back off that I can feel yet, all have remained nice and snug.
Of course, they are being takin out quite often unfortunatly and not given a real change to work themselfs loose.