Clutch No Longer Releasing - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ianepperson · 10-07-2018, 08:49 PM

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!

ianepperson · 10-07-2018, 08:57 PM

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

**Jason Banks** · 10-07-2018, 09:46 PM

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

**kwmech** · 10-07-2018, 09:53 PM

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

lil hoodlum · 10-07-2018, 10:13 PM

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.

palallin · 10-07-2018, 10:47 PM

Quote:

Originally Posted by kwmech

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

Respectfully disagree. I've used one for 25 years, now, and it has never bent anything. Given some of the things I've done with my truck, I have been very happy with the extra grab.

There can be many issues the OP is experiencing, but the mere fact of having a B&B clutch is not a problem.

weim55 · 10-08-2018, 12:40 PM

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

weim55 · 10-08-2018, 12:52 PM

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

**WorkinLonghorn** · 10-08-2018, 01:06 PM

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

Overdriven · 10-08-2018, 01:31 PM

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.

weim55 · 10-08-2018, 02:26 PM

Quote:

Originally Posted by WorkinLonghorn

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

2nd that.......

**'68OrangeSunshine** · 10-08-2018, 11:21 PM

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.

**Fbks_Cruiser** · 10-09-2018, 01:28 AM

Quote:

Originally Posted by Overdriven

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.

Flywheel shouldn’t move like that and could well be the reason for clutch not releasing.

ianepperson · 10-09-2018, 02:49 PM

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.

ianepperson · 10-09-2018, 03:12 PM

Quote:

Originally Posted by kwmech

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

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.

geezer#99 · 10-09-2018, 04:01 PM

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.

**AussieinNC** · 10-09-2018, 07:30 PM

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?

ianepperson · 10-06-2019, 11:13 PM

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.

10-07-2018, 09:46 PM	#3
Jason Banks Senior Member Join Date: Dec 1999 Location: TX Posts: 1,517	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
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,389	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

10-07-2018, 10:13 PM	#5
lil hoodlum Registered User Join Date: Oct 2009 Location: Denton, Texas Posts: 1,695	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.

10-08-2018, 12:40 PM	#7
weim55 Registered User Join Date: Jan 2017 Location: Larkspur, Colorado Posts: 904	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
weim55 Registered User Join Date: Jan 2017 Location: Larkspur, Colorado Posts: 904	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

10-07-2018, 08:49 PM	#1
ianepperson Registered User Join Date: Oct 2018 Location: Alameda, California Posts: 5	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
ianepperson Registered User Join Date: Oct 2018 Location: Alameda, California Posts: 5	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.

10-08-2018, 01:06 PM	#9
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,855	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 __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, 2nd owner, Work-Truck supreme. Best $300 I ever spent.

10-08-2018, 01:31 PM	#10
Overdriven Registered User Join Date: Mar 2016 Location: Long Island NY Posts: 598	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, 11:21 PM	#12
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,038	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. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not.

10-09-2018, 02:49 PM	#14
ianepperson Registered User Join Date: Oct 2018 Location: Alameda, California Posts: 5	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, 04:01 PM	#16
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,512	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.

10-09-2018, 07:30 PM	#17
AussieinNC Moderator Join Date: Jun 2017 Location: Cherryville, NC Posts: 2,155	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? __________________ Family and country before all others... 2006 Chevy Silverado (Daily Driver) 2012 Chevy Equinox

10-06-2019, 11:13 PM	#18
ianepperson Registered User Join Date: Oct 2018 Location: Alameda, California Posts: 5	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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