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Author Topic: Clutch won't disengage  (Read 7312 times)
jpic
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« on: June 21, 2009, 05:19:07 PM »

I'm converting from a PG to a Muncie.  I put it all together, lowered the car, and found out the clutch won't disengage.  I put in a Zoom clutch that has the raised fingers if that matters.  I torqued the pressure plate to 20 lbs.  Should I torque it to 35lbs?  Do I have the right throwout bearing in?  Any suggestions?

thanks
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hotrod68
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« Reply #1 on: June 22, 2009, 12:22:31 AM »

Sounds like the throwout bearing to me. Is it a Borg & Beck pressure plate, a 3-finger, or a raised-finger diaphragm? Google    zoomperformance.com  and ask their tech guys if you used the right throwout bearing. They can give you the right part# if you didn't. It's easy to get the throwout bearings mixed up with the different pressure plates if you don't know what to look for. I am guilty of it myself. Good luck!
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HotRod'68  1968 SS350 coupe undergoing frame-off resto/rod. 386/350/4.11s
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Stingr69
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« Reply #2 on: June 22, 2009, 06:45:11 AM »

How much free play do you have at the pedal. You can put a tape measure tip on the floor and push lightly with your fingers on the pedal pad to see how far the pedal travels before you feel resistance. The spec is about 1" of free travel.

-Mark.
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jpic
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« Reply #3 on: June 22, 2009, 09:43:15 AM »

I have lots of freeplay in the pedal when I adjust the rod that way, and none when I adjusted the rod the other way.  And I called zoom and they say the throwout bearing should be 1 1/4" long , which mine is.
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JohnZ
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« Reply #4 on: June 22, 2009, 10:03:21 AM »

Pressure plate-to-flywheel bolt torque is 35 ft-lbs., and those are special bolts with a precision unthreaded shank under the bolt head. Sounds like you have the correct throwout bearing for the bent-finger diaphragm clutch. Adjust the length of the lower rod so you have 1" to 1-1/4" of pedal free play between its fully-up position against the rubber bumper and the point where you feel resistance when depressing the pedal (which is when the throwout bearing contacts the clutch fingers). Make sure the return spring is installed correctly so the pedal is pulled up against the rubber bumper.
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'69 Z/28
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Stingr69
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« Reply #5 on: June 22, 2009, 10:26:42 AM »

I have lots of freeplay in the pedal when I adjust the rod that way, and none when I adjusted the rod the other way.  And I called zoom and they say the throwout bearing should be 1 1/4" long , which mine is.
Adjust the "other way"Huh There is no other way that I am aware of.

What did you use to align the disk while you installed the pressure plate? You need to be able to line up the disk real well so the tranny will go in all the way easily. If it is not in perfect alignment sometimes people will rest the weight of the tranny on the disk hub while they wrestle with getting the tranny aligned with the pilot bushing. That can bend the disk and prevent the clutch from releasing.

Does the car just grind going into reverse or does it not disengauge at all? What are the symptoms?

-Mark.
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jpic
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« Reply #6 on: June 22, 2009, 05:56:11 PM »

I used the correct dia. alignment tool to center everything.  I did not grind any gears when I was done with the install because I noticed right away that when I pushed in the clutch to start it, it didn't disengage and it was going to start in gear.  So I tried rocking the car with my foot on the clutch and the engine not running.  I then knew something was amiss.

I have now taken the tranny back out, and looking at how the throwout bearing is working when someone presses on the clutch.  I am just about out of rod length and I am getting the right pedal free play, but the clutch fingers seem to move about 1/4 inch.  That does not seem to be enough.  How far should the fingers flex??  Maybe I have the wrong rod??  I purchased a SB Z-bar settup but I installed a 621 bellhousing.  Maybe I need the BB setup?Huh

Thanks
Jon
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william
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« Reply #7 on: June 22, 2009, 08:28:57 PM »

With the exception of the Z/28 sb cars used an 11" clutch.

I assume this is a sb car with correct crossmember and engine mounting brackets. The Z-bar has to be perpendicular to the engine. If it has some angle, that is at least part of the problem. I believe the bracket holes are pre-punched in the frame but I have seen them off by enough to make a difference. Also, the mounting bracket is 67 only, 68-69 is different. 67-68 pedal assembly is not the same as 69, which do you have? Are you certain the release fork is correct? There were several part numbers over the years.

Just some thoughts.
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jpic
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« Reply #8 on: June 22, 2009, 10:11:16 PM »

How can you tell what  pedal assembly one has??
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Stingr69
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« Reply #9 on: June 23, 2009, 05:42:26 AM »

The 621 is fine. They were used on 350's as well as BB's so that should not be an issue. The fork needs to be right but so does the bellcrank.

I suspect your disk is in backwards. The disk spring hub is rubbing on the heads of the flywheel bolts and the extra "thickness" causes the pressure plate fingers to be already partially depressed due to the disk interfearance. Rip it all back out and verify the disk is installed properly. If this is the case, it would explain the adjustment rod being all the way out. I know that is not good news but if this is the case, it is better to know now.

William - the Z/28 used the smaller "403" setup and all the 327's did too. The 350's are a mixed bag in general with some using the "621" bellhousing and some using the "403" smaller bellhousing setup.
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Classic Gary
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« Reply #10 on: June 23, 2009, 11:05:05 AM »

just checking, did you put the clutch disc in facing the correct direction ?
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ss jim
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« Reply #11 on: June 23, 2009, 04:25:42 PM »

I second what Stingr69 said. If you have the wrong T/O bearing arm it will not allow the clutch to work properly if at all. Also the disc may be backwards but I think it would have been hard to start or tighten the bolts. Either way you will probably have to disassemble and look at it. Good luck. Jim
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jpic
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« Reply #12 on: June 23, 2009, 08:05:19 PM »

The clutch disc is in the right way (marked flywheel side), and centered.  I wonder if the fork is right.  Mine is the 14066235, but somebody mentioned the 3892632 is the one I need.  Who knows??
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ss jim
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« Reply #13 on: June 23, 2009, 09:05:42 PM »

If you are using the factory clutch, 3892632 is the correct fork. If the Zoom is what I call a "high cone" style pressure plate you will have to use another fork. I am using a Hays diaphragm 11" clutch and am using the early Corvette fork p/n 3887177. This will allow floorboard clearance. This is in a '69 SS350 w/Muncie 4 sp. If you can see inside the bellhousing (through the clutch fork hole), make sure that the T/O bearing is not against the bearing retainer. I ran into a problem similar to yours 30yrs ago with a Schiefer unit. Hope this helps. Jim
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JohnZ
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« Reply #14 on: June 23, 2009, 10:14:22 PM »

Also, make sure the throwout bearing is correctly installed on the fork - the ends of the flat spring go in the groove with the ends of the fork, not behind the flange on the bearing; the design allows it to be installed wrong.
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'69 Z/28
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