Guys,I posted this over in transmissions,but maybe someone here can help.,
1972 Mustang..302/4 speed..went from a 3 finger set up to a Zoom diaphram...at around 5000-5200,sometimes the clutch pedal won't come back up..never had this problem with the old 3 finger set up..any input? TIA..

Chris,
I had a similar problem when I swapped from diaphragm to a 3-finger (opposite of what you jsut did). I had the wrong length throwout bearing in there. Is the fork like a GM? Maybe the bearing is on the clips wrong also.

Jim,I'll have to check out that..its my neighbor's car..he installed the clutch and having the above problems..he asked me to post it.I went for a ride in it yesterday with him..it didn't do it..but he said the clutch pedal will just stay to the floor,and eventually pop up when you let off on the gas..

Gentlemen, What is happening to your clutches is your experiencing the over-centering of the pressure plate diaphram. This is a common problem with the diaphram type clutch. I had one in my 375 horsepower Chevelle that would disengage over 6000 RPM. Centrifugal force will hold the clutch pedal down once the clutch passes the halfway point and abruptly comes back up when the RPM comes down. This happened to me a long time ago while chasing a 440 GTX. The old time fix was to either put a block on the back of the clutch pedal to limit travel or go to a Borg & Beck type clutch which required a strong left leg. One of the good clutch manufactures should be able to suggest a better fix than changing to a B&B type clutch.

By the way 5200 RPM is pretty low to be having this problem as my 442 never stuck the clutch an could turn 5500-5800 without a trace of trouble.

Harold,my neighbor said it did this at 2000 rpms with just the one factory spring that holds the clutch adjustment rod in place..he added a few more springs and now it does it at 5000 rpms..any ideas? Jim,I wondering if the Zoom kit he bought came w/the wrong throw out bearing?

Chris,
It has nothing to do with the springs, and everything to do with clutch travel. If you push a diaphram clutch in too far, you will have the problem. You can put more free play in the adjustment so that the clutch just barely disengages at the floor, or you can put a stop behind the pedal to keep it from going too far. Somewhere in the service manual, and probably in your clutch instruction sheet, there is a spec for how much gap there should be between the clutch disc and the flywheel when the pedal is all the way down. This is the adjaustment that needs to be corrected.

If I'm not mistaken the leverage ratio of a finger type clutch is greater than a diaphram type, requiring more linkage travel to disengage. Likely the linkage geometry is designed to provide this increased travel as the "long" style clutch is the standard deal in Fords. If that is the case either a stop under the clutch pedal, (a block as was mentioned earlier) or adjusting for more freeplay might do the trick. As long as the clutch will release cleanly for shifting more freeplay will not hurt anything.

If your bellhousing will allow it try to measure the air gap between disc and flywheel with the clutch pedal on the floor. I think .060" to .070" is the number for a diaphram type. My guess is you have way more than that and are overcentering the diaphram.

Regards,
Gary Anderson

Originally posted by BillK:
Chris,
It has nothing to do with the springs, and everything to do with clutch travel. If you push a diaphram clutch in too far, you will have the problem. You can put more free play in the adjustment so that the clutch just barely disengages at the floor, or you can put a stop behind the pedal to keep it from going too far. Somewhere in the service manual, and probably in your clutch instruction sheet, there is a spec for how much gap there should be between the clutch disc and the flywheel when the pedal is all the way down. This is the adjaustment that needs to be corrected. BillK has the correct answer to your problem. With a diaphragm clutch, there should be only about .030 clearance between the disk and flywheel when the pedal is all the way down. A way to check the clearance is to put a .030 feeler guage between the disk and flywheel so that when the pedal is fully depressed the feeler guage will drop out from its own weight. The other way is by trial and error, adjusting the clutch so it just releases when the pedal is on the floor. You may want to put a real stiff return spring on the linkage so the pedal comes all the way to the top and you can feel some resistance when your foot is on the clutch pedal.
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Jon N.

Guys,thanks for the info..I will pass it along graemlins/thumbsup.gif smile.gif