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Clutch problems

7

78C20Reaper

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Hi all first off if this is in the wrong section I apologize. If this specific issue has been addressed before I couldn't find it, I did search a bit first. I have a 1978 c20 with a 350/sm465 (I believe) combo. The shift knob goes L-1-2-3-R. But anywho I've been having clutch issues the last couple days.

With the pedal on the floor i start it in gear just like i park it and it tries to roll, not alot but enough to notice. At a standstill with engine running it will grind and grind like the clutch isn't released with the pedal on the floor.

I read the manual from autozone and attempted to adjust the manual clutch setup but I either did it wrong or that's not what it needed. Also as soon as I let off the pedal any the clutch starts to grab hard and bog the truck down. I know it should bog down with the clutch engaged but it used to start an inch or two off the floor not just letting pressure off the pedal.

I'm new to mechanical clutches and old school tech so I'm tackling two new things at once. I apologize if that is confusing and I can and will explain better if needed. Any help is appreciated and thank yall in advance
 
Last edited by a moderator:
The inch or two off the floor is where you want it.

If it was like that before your adjustment, go back where it was plus a little
 
So the “L” gear is not synchronized, it will usually grind a tad until you learn the feel the gear in the shifter

I actually like the clutch up further. I’ll see if I have a pic of where mine is. Excluding a mechanical issue, it should get you in the ball park
 
I did try to do some research and I did learn that the low and reverse gears are not synchronized but it grinds hard trying to go into any gear. With the engine off all the gears are super hard to go into and the more I drive it the harder it is to shift going down the road. I've had the truck for about 8 months and a few other standards but I've never had one bruise my hand because it refused to go into gear
 
I was afraid you were gonna day that, which is more indicative of the clutch not disengaging

see if you can get the pedal further off the floor first
 
I ran the adjuster rod a good probably 1/2 inch and it didnt change anything. I moved it both ways and found the wrong way when I started since the book didnt tell me which way to go. I was adjusting a little and testing it also but it never changed
 
You want about 3/4" of free play at the pedal when you depress it ,before you feel any resistance..
If adjusting it to that spec still fails to stop the grinding,then my guess is the pressure plate is not fully releasing..
The ones that have "3 fingers" often fail in this manner,one of the fingers fails to disengage the pressure plate ,usually you will get clutch chatter too when this happens..

I had bad luck with 3 of the 12" 3 finger style pressure plates,I went to a diaphragm type one after the third time I had to pull the transmission & transfer case out..
 
I have slight resistance starting about an inch down but the feel hasn't changed much which is throwing me off. I thought about just putting a new clutch kit in it because who knows how long the current has been in it and I'm not exactly the easiest on my vehicles so I was looking at getting a heavy duty plus big trailers need big clutch right? How would I know which type of pressure plate I have? Would I have to drop the tranny? I'm sorry if these seem like dumb questions but I'm new to old school and the mechanical clutch setup.
 
I'll elaborate on the clutch feel part since I realized I left that out. Pressing the clutch down feels almost the same, slight resistance at first and it increases farther down. Where it's not the same is the release as it tries to engage with the pedal still touching the floor. And last night a new thing happened, the pedal stayed about 2 inches off the floor and I had to pull it back up with some force. Not just shove your foot under it force but coast to a pull off spot, get out and grab it kind of force.
 
That's not good...could be the throwout bearing is not able to slide freely on the collar it sits on ,that is over the transmission's input shaft,or the clutch disc might be sticking on its splined hub that rides on the input shaft,or the pressure plate may have damaged or broken fingers and pieces are getting wedged in it..

I had the anti-chatter springs fail on a clutch disc once ,and they got wedged in the pressure plate fingers,and the clutch refused to release..

You should check all the bolts holding the transmission & bell housing on,if they loosen up enough the transmission can sag,and cause the pilot bushing to keep turning the input shaft with the pedal pushed down,or make the throwout bearing get hung up on the collar it rides on..

Another uncommon issue I ran into on one truck I had that had rotted cab mounts,the cab would rise up and down when I pushed the clutch pedal down,and released it..that movement reduced the travel of the linkage and throwout bearing,and the gears would grind..
After I rigged up some cab support,it went back to working normally..

I would plan on getting a new clutch setup--usually when these kind of issues arise,its not often a simple adjustment or what I've advised to do will cure the problem..
 
I will definitely check the bolts. Could the tranny mount cause the same issue? It looks a little dated (cracks from age and what have you) but it's still all there. Would I be able to tell if there is any transmission sag by looking at the driveshaft angle? I have the two piece shaft with carrier in the middle also.
 
The bolts holding the transmission to the bell housing and the bell housing bolts would be the most likely ones to cause issues--the transmission mount if bad, may let the whole engine/transmission assembly sag as a unit,but that probably wouldn't affect the operation of the clutch much if at all..it might cause vibrations if the u-joint angles got changed as a result though..
 
Well I guess I'm gonna need to save up a little bit after this whole beerflu thing is over with to buy a clutch kit. I checked all the bolts I have sizes for in my truck and they were all tight. Any advice on adjustments once I get the new clutch in?
 
I just adjust them until it has the 3/4" of free play...

You say you had to forcefully pull the pedal back up bu hand in one post--I would make sure all the clutch linkages aren't rubbing against something or binding up in that case,check the "Z bar" bell crank thing thats riveted to the frame ,see if it has bent the levers or has a sloppy bushing--and no return springs are missing or broken,came off,etc..however,that will not affect the free play or amount of travel at the pressure plate unless something is really sloppy or broken,but it is worth investigating...you may get lucky..
 
This is the Z bar--I have seen a few have the levers bend ,changing the amount of offset & throw the linkage needs ,and cause issues..and adjusting the clutch wont fix that if it is the cause--also if the balls it rides on at the frame and engine block get sloppy it can cause issues too..clutch z bar.png
 
Which is the "Z bar"? I did have to take the adjuster rod setup off to break it loose. While I had it off I had my room mate press the clutch pedal a few times and it looked like it moved pretty freely. Also it didnt stick down with the adjuster rod setup off.
 
78C20Reaper said:
Which is the "Z bar"? I did have to take the adjuster rod setup off to break it loose. While I had it off I had my room mate press the clutch pedal a few times and it looked like it moved pretty freely. Also it didnt stick down with the adjuster rod setup off.
Click to expand...
The Z bar is basically a tube with 2 levers welded to opposite sides of the tube. The linkage rods hook to the levers.

The picture that @diesel4me posted probably isn't visible to you. Only premium membership will be able to see some pictures unless hosted by another source.
 
Just type in "Chevy Truck Z Bar" on google and click "Images",he'll see it then...
 
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