Author Topic: Looking for clutch adjustment problem help  (Read 882 times)

jmcbeth

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Looking for clutch adjustment problem help
« on: September 08, 2021, 12:43:25 AM »
Looking to see if anyone else has seen this problem and has suggestions. This is a full restoration of a 1969 Camaro Z/28. Engine rebuild (DZ), shifter rebuild (Hurst Competition Plus). New clutch, pressure plate, GM clutch fork (GM part number 3892632), throwout bearing. Verified the following are all correct: clutch fork pivot ball (short one), adjusting rod, bell crank, clutch pedal, upper clutch push rod.

The problem is that there is not enough travel in the clutch pedal. There should be play at the top of the clutch pedal travel (foot off the pedal to engagement of the throwout bearing) and play at the bottom of travel (pedal pushed to the floor) before the clutch engages. The best I can get is no play at the top of travel (i.e., throwout bearing is against pressure plate fingers) and the clutch begins to engage at the floor. Seems like pressing the clutch pedal does not pivot the clutch fork enough. Any ideas?
John
1969 Camaro Z/28 RS
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Kelley W King

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Re: Looking for clutch adjustment problem help
« Reply #1 on: September 08, 2021, 11:56:14 AM »
I would have someone work the pedal while you watch the movement of the clutch fork. Even new parts have problems. There are different cross bars that look the same until you compare them, that is what I would suspect first. The length of the bars off the round part could be wrong affecting the travel.
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janobyte

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Re: Looking for clutch adjustment problem help
« Reply #2 on: September 08, 2021, 01:09:00 PM »
Just throwing it out there.
I noticed the repro pedal return spring was weak. Wasn't pulling the pedal to the upper stop,,thus throwing my adjusment off. Was probably loosing a good inch off the top.
68 Z/28  born with: 302, drive line, etc..

janobyte

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Re: Looking for clutch adjustment problem help
« Reply #3 on: September 08, 2021, 01:10:26 PM »
And also what KK said above.
68 Z/28  born with: 302, drive line, etc..

jmcbeth

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Re: Looking for clutch adjustment problem help
« Reply #4 on: September 09, 2021, 10:24:16 PM »
All, thanks for the ideas. Per recommendations above, with the help of a friend I was able to measure the movement of the adjustment rod end of the clutch fork from the pedal  rest position to the fully depressed position. The end of the fork moved 1 inch. I used the front edge of the bell housing as the reference point. I have the luxury of having a reference car, which measured 1-3/8 inches for the same test. Anyway, I pulled the cross bar (pain in the butt) and compared it to the original from the car (which I do not think is the original one from the factory). They were indeed different, although subtly. The angle between the two arms was different and the adjustment rod arm was longer. However, the distance from the round part to the holes in both arms seemed almost identical. I installed the old bar and still have the same problem.

I also have a repro spring and it is weak, but I am careful to pull the pedal up with my foot before drawing any conclusions.

Next step is to order a new cross bar. I just ordered part # TRN-1002 from Heartbeat City. This should be the replacement for GM part number 3899013 (Assembly Manual UPC 7, C3, part 1).

Again, thanks for the suggestions. They confirm I am on the right track. Seems like the only real way to change the range of motion of the clutch fork is to change the radius of one of the cross bar arms on the cross bar. Specially, the rod hole needs to be closer to the round part. Sound right?

One other fact: when I disassembled the car for the frame off restoration, it had a scatter shield. However, the clutch fork was identical to the GM part.
John
1969 Camaro Z/28 RS
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olddragracer

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Re: Looking for clutch adjustment problem help
« Reply #5 on: September 10, 2021, 07:57:08 PM »
   Reduce the thickness of the clutch pedal stop bumper. That will give the clutch pedal more travel and give the clutch more release. When the clutch has some wear a new bumper can be installed. This solution was used often when these cars were current

jmcbeth

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Re: Looking for clutch adjustment problem help
« Reply #6 on: September 15, 2021, 12:39:18 AM »
Well, just got the “correct” cross bar. It’s identical to mine. Therefore, not the problem. I like oldragracer’s suggestion and will try that next. Thanks!
John
1969 Camaro Z/28 RS
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Kelley W King

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Re: Looking for clutch adjustment problem help
« Reply #7 on: September 15, 2021, 12:24:22 PM »
I think you said your clutch fork was new but I have had one that had a crack that was not noticible but let the fork flex under pressure. I believe we could see it through the dust boot hole. Try the stop first.
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ko-lek-tor

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Re: Looking for clutch adjustment problem help
« Reply #8 on: September 15, 2021, 08:29:42 PM »
My experience is that the clutch fork pivot ball and or throw out bearing are the culprits. The stock height ball worked great on my diaphragm press. plates. When I switched to a 3 finger Borg Beck style, the alignment and adjustment problems began. I ended up getting a longer fork pivot ball that gave more distance and , therefore,  adjustability to pedal. There are different heights of throw out bearings as well
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jmcbeth

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Re: Looking for clutch adjustment problem help
« Reply #9 on: September 27, 2021, 01:06:18 PM »
PROBLEM SOLVED! I removed the clutch pedal stop and am now able to adjust the clutch to get the range of motion required. I actually drove the car in the neighborhood for the first time this morning.

I found the original stop and it was indeed much thinner than the new replacement stop. It looks like someone had cut the original stop.

Thanks to everyone for their suggestions. A special shout out to olddragracer for the ultimate fix. Now on to other adjustments and fine tuning…
John
1969 Camaro Z/28 RS
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