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10-07-2018, 08:49 PM | #1 |
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Join Date: Oct 2018
Location: Alameda, California
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Clutch No Longer Releasing
Hi everyone! I created an account to see if I can get some advice on an issue I'm having.
The truck is a 1970 Chevy C/20, originally with an HD clutch (among other factory upgrades - my dad (RIP) had ordered it from the factory with a bunch of additions). 1st gear is a granny gear. The engine has been replaced and my mom tells me that she had someone "replace the clutch" just a few years ago. I borrowed the truck for a desert camping trip, and it ran like a top for a few hundred miles up and back, then 5 miles from home it won't go into gear. It's as if pushing in the clutch pedal does nothing - 1st gear grinds (non-syncro) and no other gear will slide in. I managed to hot-shift for the last few miles and started looking at it. There was no pop or breaking sound, and there's no additional noise coming from the housing. I read that the linkage sometimes gets badly worn. I had about 1/2 of thread to tighten it up and noticed that the arm protruding from the bell housing has two positions to land the linkage, and it was on the outer (easier pedal, less travel?). I moved it to the inner (slightly harder pedal, more travel) and tightened up the push-rod to snug it up, but it didn't seem to make any difference. I pulled the lower inspection plate to look at the pressure plate today. Everything looks OK, but I'm not familiar with this setup. I did notice that when I had my son press the clutch the flywheel moved forward about 1/16" - is that normal? I was able to pull it back by hand. I reached up and felt the throwout bearing - it seemed correct and I was able to spin it with my fingertips. It did feel as if there was more space than I imagined - perhaps the pressure plate is missing a finger? I didn't want to miss my own fingers so didn't feel it as my son pressed the pedal. I did see the pressure plate slightly move off the clutch plate, but perhaps not enough? Any advice would be greatly appreciated. Thanks! |
10-07-2018, 08:57 PM | #2 |
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Location: Alameda, California
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Re: Clutch No Longer Releasing
Here's a video of what I saw under the inspection plate:
https://www.icloud.com/photos/#0yleV...4skMpQGRvz4kIQ And again on Youtube because Apple is trying to rule the world: https://youtu.be/18-FL0yG138 Last edited by ianepperson; 10-09-2018 at 02:48 PM. |
10-07-2018, 09:46 PM | #3 |
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Join Date: Dec 1999
Location: TX
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Re: Clutch No Longer Releasing
From what I could see in the video. It looked like it was working properly. I would #1 check fluid in transmission. #2 It's not a whole lot of work to pull the drive shaft and transmission to check everything out.
Edit to add...to check the fluid, remove the plug and make sure fluid is up to top of plug hole. Or...just add fluid until it starts running out of the hole |
10-07-2018, 09:53 PM | #4 |
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Re: Clutch No Longer Releasing
If the clutch is too "heavy duty" then you could possibly bend the bar that passes through the firewall to the bell crank. No reason to have a 3 finger borg and beck style in a truck. An 11'' diaphragm clutch will grab plenty
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10-07-2018, 10:13 PM | #5 |
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Location: Denton, Texas
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Re: Clutch No Longer Releasing
The clutch isn't releasing allowing you to shift the gears as needed. Sounds as if you need to adjust the clutch.
My clutch does the same thing and I will have to adjust the free play in the clutch to allow it to fully release from the flywheel. Look up adjusting clutch pedal free play. |
10-07-2018, 10:47 PM | #6 | |
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Re: Clutch No Longer Releasing
Quote:
There can be many issues the OP is experiencing, but the mere fact of having a B&B clutch is not a problem.
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10-08-2018, 12:40 PM | #7 |
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Re: Clutch No Longer Releasing
If all of your symptoms are complete and correct the problem points to a bad support bearing in the back of the crankshaft for the input shaft. The input shaft is seized in the bearing. To test this put the transmission in neutralwith the clutch pedal pushed and held at the floor, get under the truck and attempt to turn just the clutch disc. You should be able to do this with a sharp pick or screwdriver. If the clutch is releasing properly and the clutch disc will not move the support bearing is bad in the back of the crank for the input shaft. This would cause the exact problems you're describing.
Steve weim55 Colorado |
10-08-2018, 12:52 PM | #8 |
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Re: Clutch No Longer Releasing
Moving towards the rear of the truck from that support bearing a couple other issues could create the same problem: cracked and broken pivot socket on the clutch fork ( most common) failure in the pressure plate not allowing the clutch to fully release ( most common number 2), broken collar on the input retainer that the throw out bearing slides back-and-forth on ( very uncommon)
Steve weim55 Colorado |
10-08-2018, 01:06 PM | #9 |
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Re: Clutch No Longer Releasing
It really doesn't matter what you feel, see or hear. If the clutch linkage is functioning and the clutch isn't releasing, that transmission has to come out so's you can have a look-see. -BA
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10-08-2018, 01:31 PM | #10 |
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Re: Clutch No Longer Releasing
I couldn’t see the video because I’d have to download and I’m on iPhone right now.
Anyone else not like the fact he can see his flywheel move 1/16 of an inch? Crankshaft end play shouldn’t be that much and I kind of doubt it is. I’m wondering if whoever replaced the clutch had the flywheel resurfaced, didn’t use lock tight on the flywheel bolts and now they’re loosening. While probably not the source of the clutch not releasing it is something that should be addressed. |
10-08-2018, 02:26 PM | #11 |
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Re: Clutch No Longer Releasing
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10-08-2018, 11:21 PM | #12 |
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Re: Clutch No Longer Releasing
On a couple of my trucks, I've had a problem with one of the arms of the Z-bar breaking off or slowly bending until breaking. Admittedly I have had the arms bent to clear headers.
But on a 50 year old vehicle metal fatigue is common, especially when in heavy use like a daily driver. I had exactly the gripe you're describing, just before my Z-bar lost an arm. Over a period of a few months I had to gradually add length to the clutch pushrod to get the throw-out bearing to disengage. It finally broke in rush hour traffic on the way to work. I had to bail from a job and get towed home. Once in my carport, I pulled the Z-bar pieces and took them to a welder buddy. Look closely at the joins of the arms on the Z-bar at the junctions of the upper clutch rod and [lower] clutch pushrod. "Z-Bar" is slang for the clutch thrust bellcrank, if you're new at this.
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10-09-2018, 01:28 AM | #13 | |
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Re: Clutch No Longer Releasing
Quote:
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10-09-2018, 02:49 PM | #14 |
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Location: Alameda, California
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Re: Clutch No Longer Releasing
Thanks for all your responses!
Here's the video on Youtube: https://youtu.be/18-FL0yG138 I'm used to working on old VWs and the end play seemed way excessive to me, but I'm not nearly as familiar with this engine. I only have another weekend day or two to work on this before the holiday season strikes - and unfortunately I can't easily get it into a garage. If it's not a simple fix I may just pay someone to do the work. Meh. I'll check and top up the fluid as Jason_Banks recommended, then I suppose I'll pull the entire linkage and check it carefully. I'm guessing I'd have to do that anyway to pull the transmission. |
10-09-2018, 03:12 PM | #15 |
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Re: Clutch No Longer Releasing
Dad had special ordered this truck from the factory with HD clutch, HD radiator, HD suspension, power steering, power brakes, camper package, and more. He then bought a new cabover camper and every summer throughout the 70s and 80s we'd head out camping in the over full truck. He passed away in '99 and mom has been using the truck since. I suspect that over the last 20 years whenever someone did any major work on the truck, mom had just indicated that the clutch is the best and should stay that way - even though she can't drive it anymore because her knees are too weak to articulate the clutch. If I have to replace it, it's likely getting a diaphragm pressure plate so that she can at least drive it.
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10-09-2018, 04:01 PM | #16 |
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Re: Clutch No Longer Releasing
From your video I’d say you have more trouble than just your clutch. That much movement in the flywheel suggests the thrust bearing is shot in the motor.
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10-09-2018, 07:30 PM | #17 |
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Re: Clutch No Longer Releasing
Check that the front balancer is also moving back and forth the same amount as the flywheel....if it is, the thrust face of the rear main bearing has collapsed and worn out....
If the balancer does no move back and forth the same amount as the flywheel, it can be two issues...most likely the flywheel is loose on the crankshaft. Worse case if the flywheel is not loose, I have seen a broken crankshaft on the last web do exactly what is shown in the video. I also suspect the pressure plate is a diaphragm type now, as it doesnt look like a Borg and Beck cover...(to these old eyes)....if it has been swapped over to diaphragm type...and the release bearing was not changed from Borg and Beck to diaphragm type....the clutch will not achieve release. (The diaphragm type release bearings are taller than the Borg and Beck). I have also seen a release bearing tightened up solid against the release fingers and burn right thru the fingers...but I suspect you have several issues... Crank end play is way too excessive Suspect release bearing is wrong height Clutch Z bar may have bent arms Clutch diaphragm spring has collapsed Simplest way to accurately diagnose, pull the transmission out and the clutch... remove flywheel and check for broken crank flange...(grab it and wriggle it)... if it moves at all...pull the engine.... Post pics once you get the trans out.... BTW...if this was a mechanics shop that replaced the clutch, does the work come with any warranty?
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10-06-2019, 11:13 PM | #18 |
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Location: Alameda, California
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Re: Clutch No Longer Releasing
Thank you for everyone's help. The clutch pressure plate had broken, and while replacing the clutch (quite the pain!) we found that the end-play is indeed somewhere around 1/8" - so the engine needs to come out regardless for a rebuild. Instead, I'm selling the truck.
https://sfbay.craigslist.org/eby/cto...994232035.html If interested. |
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