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I have a 79 Corvette with a T-10. The clutch had about 10,000 miles on it and then I pulled the car apart for a 2 year restoration. I now have it all together and had retained the same clutch, pressure plate and fly wheel as it only had 10,000 miles on it and still looked new. When I first got it all together everything worked perfectly but when I drive it the clutch keeps coming out of adjustment. If I adjust it so that the peddle releases the clutch when the pedal is between 1 1/2 to 2 in off the floor everything is fine but after about 80 miles the clutch pedal will have to be on the floor to release and will drag. I have gone threw this about 4 times and it is not the push rod that is coming out of adjustment, that is all staying in place. What could be going on?
is the nut that holds the z bar to the frame bracket loose? have you had anybody step on the clutch while you were under the car to see if anything is moving that shouldnt be?
As the friction material on the clutch disk wears, the clutch pedal freeplay will decrease and will need readjustment. You should have about 1 1/2" of clutch pedal freeplay from the top until the throwout bearing contacts the fingers of the clutch. You can feel this by moving the pedal downwards by hand with the engine running in neutral.
Are you sure the TO bearing was installed correctly?
So I got under the car tonight and had my wife work the clutch and did not see any play or movement any where. I used a after market clutch linkage and everything was tight but I did notice that the bracket that attaches to the clutch fork looked like it might have moved slightly. it was tight but I repositioned it and checked the clutch and it did not make much difference. I did marked it to see if it moves. May have to just weld it in place if it does move.
I again adjusted the clutch so that it releases about 1 1/2 from the floor and has about 1 in of free play. I am going to drive it to work tomorrow which is a 80 mile round trip and see what happens. I am worried that it could be something to do with the clutch fork pivot ball.
As the friction material on the clutch disk wears, the clutch pedal freeplay will decrease and will need readjustment. You should have about 1 1/2" of clutch pedal freeplay from the top until the throwout bearing contacts the fingers of the clutch. You can feel this by moving the pedal downwards by hand with the engine running in neutral.
Are you sure the TO bearing was installed correctly?
I am sure the TO bearing is installed correctly. When I adjust everything it works just fine for about 75 to 100 miles.
I am stumped with what is wrong. I drove to work today and by the time I got home the clutch was again out of adjustment. Re adjusted it and took the car to a road course and did 6 runs, about 2 miles for each run, but after the 4th I had to re adjust it again and on the last run I got stuck in 2nd gear. Now I am out of adjustment.........now what?
Have you checked the condition of the pins under the dash, connecting the pedal arm? Mine exhibited some similar behavior. Funny thing, one of pins in mine just fatigued and broke yesterday afternoon, leaving me in the middle of an intersection. Upon checking, all of the remaining pins were severely worn and in need of replacement including the push rod shaft. You have to keep telling yourself that the metal in these cars is in the neighborhood of 40 years old.
The pin that is welded on the clutch pedal gets worn down. It is a hardened pin. Once the outer layer gets worn away, the rest of the pin will wear faster and then break sending you and the car flying forwards.
I don't think this is your problem but check it anyways. Changing this pedal is a major pain BTW.
Just curious, why did you go for an aftermarked set-up for this?
Have you checked the condition of the pins under the dash, connecting the pedal arm? Mine exhibited some similar behavior. Funny thing, one of pins in mine just fatigued and broke yesterday afternoon, leaving me in the middle of an intersection. Upon checking, all of the remaining pins were severely worn and in need of replacement including the push rod shaft. You have to keep telling yourself that the metal in these cars is in the neighborhood of 40 years old.
Less than 1000 miles on the car since everything was apart and replaced the clutch/brake pedal bushings. I took a look at everything just now and 0 play and everything is tight.
The pin that is welded on the clutch pedal gets worn down. It is a hardened pin. Once the outer layer gets worn away, the rest of the pin will wear faster and then break sending you and the car flying forwards.
I don't think this is your problem but check it anyways. Changing this pedal is a major pain BTW.
Just curious, why did you go for an aftermarked set-up for this?
steve L
73 coupe since new.
The car was a auto car and when I changed it over to a manual I decided to use the aftermarket linkages so there is less flex. I so no flex when some one pushes the clutch pedal with me under the car.
Its got to be something in the bell housing. I hate to pull the transmission just to check.
I just installed my z bar last night. Looking at your photos, I see that you have heim joints for the lower part of the z bar. Are you using this to adjust the pedal travel? Because a stock C3 has a solid bar there instead and the pedal adjustment is made at the top link.
In your first post, you mentioned adjusting the clutch so that it releases 1" or 1 1/2" from the floor. Usually, I adjust it, as to how loose the pedal travel is at the top and let the clutch assembly 'decide' where it's going to release.
Next, is the clutch pedal spring removed, when you are doing these adjustments? You can get a really good feel, for the right amount of pedal slack at the top, with the spring not on there.
Finally, you might even be getting binding, using that threaded shaft, with the heim joints. The factory set up uses free floating pins, that are secured with cotter pins and on mine, I use the spring loaded type, that are easily removed by hand. Makes it handy when you have to remove the oil filter, just pull the cotter pin and the lower linkage swings away.
Hope this helps, as I was just doing this last night!
I have a 79 Corvette with a T-10. The clutch had about 10,000 miles on it and then I pulled the car apart for a 2 year restoration. I now have it all together and had retained the same clutch, pressure plate and fly wheel as it only had 10,000 miles on it and still looked new. When I first got it all together everything worked perfectly but when I drive it the clutch keeps coming out of adjustment. If I adjust it so that the peddle releases the clutch when the pedal is between 1 1/2 to 2 in off the floor everything is fine but after about 80 miles the clutch pedal will have to be on the floor to release and will drag. I have gone threw this about 4 times and it is not the push rod that is coming out of adjustment, that is all staying in place. What could be going on?
You say that the push rod isn't coming out of adjustment, then what do you adjust to get it back into correct adjustment? Are you calling the rod from the Z bar to the clutch fork the push rod? I don't understand
Last edited by T-TOP TOM; Sep 19, 2014 at 11:43 PM.
You say that the push rod isn't coming out of adjustment, then what do you adjust to get it back into correct adjustment? Are you calling the rod from the Z bar to the clutch fork the push rod? I don't understand
So I just keep lengthening the push rods to get the clutch pedal back up into adjustment to release the clutch. The clutch will work for maybe 80 miles but the release point slowly gets closer to the floor until I can not release it any more.
So the complete set up is a 11 in Hays billet steel flywheel, Centerforce II clutch with centerforce TO bearing, a new clutch fork and a adjustable clutch fork pivot ball and a GM 621 bell housing.
When it is adjusted it works really well, no slipping, smooth and no chatter.
I just installed my z bar last night. Looking at your photos, I see that you have heim joints for the lower part of the z bar. Are you using this to adjust the pedal travel? Because a stock C3 has a solid bar there instead and the pedal adjustment is made at the top link.
In your first post, you mentioned adjusting the clutch so that it releases 1" or 1 1/2" from the floor. Usually, I adjust it, as to how loose the pedal travel is at the top and let the clutch assembly 'decide' where it's going to release.
Next, is the clutch pedal spring removed, when you are doing these adjustments? You can get a really good feel, for the right amount of pedal slack at the top, with the spring not on there.
Finally, you might even be getting binding, using that threaded shaft, with the heim joints. The factory set up uses free floating pins, that are secured with cotter pins and on mine, I use the spring loaded type, that are easily removed by hand. Makes it handy when you have to remove the oil filter, just pull the cotter pin and the lower linkage swings away.
Hope this helps, as I was just doing this last night!
I see what you are saying about it binding but being under the car while some one cycles the clutch the lower push rod can be twisted a lot and I think has more range of movement than stock. I do like the thought of being able to quickly remove the stock one to change the oil filter.
I also usually adjust the clutch by measuring the free play as you do but I was trying to just give a point of reference to how the release point of the clutch keeps moving.
I may have to just pull everything apart but really don't want to. I have my daily driver also apart so to many vehicles down now and having to use my wife's Suburban to get to work. I also want to get the vette working again quickly because winter is almost here and after going 2 years with the car apart I want more than just a few months to drive it before it winter storage time.
This is the push rod from the clutch pedal to the Z bar.
This is when I was assembling the car and before it was ever adjusted, but now I am out of adjustment both here and at the lower push rod.
I will take some pics of the factory top link and post it tomorrow morning. That rod, coming from the clutch pedal , to the top of the z bar, isn't factory either and that bolt is a good deal smaller than the factory dowel that pushes through the same hole. You mention both adjustments, upper and lower, but on the factory setup, it's done only on the upper.
I understand that is how you got the car, but that whole setup, may now be suspect. By having a bottom adjustment, that was never there in the first place, you may be altering the geometry of the clutch linkage.
This is the push rod from the clutch pedal to the Z bar.
This is when I was assembling the car and before it was ever adjusted, but now I am out of adjustment both here and at the lower push rod.
Here is the factory upper linkage. Compare what's on yours and the factory one, is way burlier and fills the whole hole. I'd recommend going back to the factory set up. It's not weak by any means.
Here is how the lower set up, factory, heavy steel bar, it'd take a lot to bend that! Note, what we were talking about, with the easy-to-remove clips, so you can swing it out and get out the oil filter. Another trick we do, is to put a tent over the exhaust pipe underneath, made out a sheet of aluminum foil, so no oil gets on the pipe. Cheap, disposable and easy.
This is the lower z bar linkage. Note how the end meshes into the throwout bearing arm and the big pivot. Tight tolerances there too, horizontal and vertical, but able to move freely in the direction it's supposed to. Good engineering on GM's part there, as they're pretty tough, right from the factory.
Here is the factory upper linkage. Compare what's on yours and the factory one, is way burlier and fills the whole hole. I'd recommend going back to the factory set up. It's not weak by any means.
Here is how the lower set up, factory, heavy steel bar, it'd take a lot to bend that! Note, what we were talking about, with the easy-to-remove clips, so you can swing it out and get out the oil filter. Another trick we do, is to put a tent over the exhaust pipe underneath, made out a sheet of aluminum foil, so no oil gets on the pipe. Cheap, disposable and easy.
This is the lower z bar linkage. Note how the end meshes into the throwout bearing arm and the big pivot. Tight tolerances there too, horizontal and vertical, but able to move freely in the direction it's supposed to. Good engineering on GM's part there, as they're pretty tough, right from the factory.
Thank you for the photos. I decided to pull the transmission this afternoon and it was the adjustable pivot ball. It was as far down as it could go. I set it back up and welded it so I don't have to worry about this being a problem again. Got the transmission back in but need to get header gaskets before I can take it for a drive. I may go to factory linkages but one change at a time.
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Clutch not staying in adjustment
