Clutch disengagement Solution
Thread Starter
Pro
Joined: Jan 2010
Posts: 518
Likes: 12
From: Panhandle
Clutch disengagement Solution
Doing a 1974 auto trans to 4 spd swap. Of course, I'm having clutch disengagement & lack of free play problems. Been reading all the forum clutch posts. All are helpful. JustinD's clutch disengagement problem with 224 posts was of great assistance. Although, he resolved the problem by installing a hyd clutch, I'm determined to peel the onion till it works as designed. Red 71, provided very useful objective information. He said, "Now if you lay the z-bar on a flat surface it should want to lay with the clutch fork rod end sticking up in the air. The measurement from the flat surface up to the centerline of the hole is 2 ¾” Mine is 3-5/8" See photo.
Also he said when describing the clutch fork, "Position the fork on a flat surface as it appears in the picture. Press down on the two fingers where the TO bearing attaches so the fork can not wobble. Measure up from the flat surface to the center of the hole that the pin goes thru. The distance should be 4 5/16”. I just measured a new GM part# 3887177 fork to verify that measurement. Just measure mine and it is 4 - 1/8" a quarter of an inch shorter. see photo.
Can someone verify my measurements of Red 71's dimensions?
I suspect the person who had the clutch kit which I purchased experienced problems and eventually sold it. One sign is a hole drilled beneath the OEM hole. See photo.
Would gladly replace the Clutch Fork and ZBar!
Also he said when describing the clutch fork, "Position the fork on a flat surface as it appears in the picture. Press down on the two fingers where the TO bearing attaches so the fork can not wobble. Measure up from the flat surface to the center of the hole that the pin goes thru. The distance should be 4 5/16”. I just measured a new GM part# 3887177 fork to verify that measurement. Just measure mine and it is 4 - 1/8" a quarter of an inch shorter. see photo.
Can someone verify my measurements of Red 71's dimensions?
I suspect the person who had the clutch kit which I purchased experienced problems and eventually sold it. One sign is a hole drilled beneath the OEM hole. See photo.
Would gladly replace the Clutch Fork and ZBar!
Thread Starter
Pro
Joined: Jan 2010
Posts: 518
Likes: 12
From: Panhandle
Zbar Update
Thanks to DZRick's post, it is easy to see my Zbar is NOT the right part for a Vette.
Here is a photo of my Zbar (bad one) installed. Notice the angle.
Here is a picture of what it should look like --check the angle. Not sure where the photo came from.
Here are two photos which show the two Zbar angles
Also suspect the exagerated angle on my Zbar/clutch fork rod caused damage to the Clutch fork throw-out bearing spring. See in photo how the spring is deformed.
As stated in the inital post, the fork at the clutch rod is bent and 3/16 shorter than what it should be.
Yes! my clutch geometry was way off, I'm guessing about one inch or more. It is no surprise the previous owner of the Zbar tried to make it up by drilling a hole under the original clutch pedal rod to Zbar.
Well now I'm going to buy a new Clutch Fork and Zbar!
When I get it, I'll install the parts and see what other challenges lie ahead. Still suspicious is the Clutch fork pivot bolt which is 1.5" with a OEM 1.2" flywheel and NOT .96"? I think it should be a 1-3/8".
My success is a tribute to all who took the time to post. Special thanks to Red 71, JustinD, and DZRick.
Here is a photo of my Zbar (bad one) installed. Notice the angle.
Here is a picture of what it should look like --check the angle. Not sure where the photo came from.
Here are two photos which show the two Zbar angles
Also suspect the exagerated angle on my Zbar/clutch fork rod caused damage to the Clutch fork throw-out bearing spring. See in photo how the spring is deformed.
As stated in the inital post, the fork at the clutch rod is bent and 3/16 shorter than what it should be.
Yes! my clutch geometry was way off, I'm guessing about one inch or more. It is no surprise the previous owner of the Zbar tried to make it up by drilling a hole under the original clutch pedal rod to Zbar.
Well now I'm going to buy a new Clutch Fork and Zbar!
When I get it, I'll install the parts and see what other challenges lie ahead. Still suspicious is the Clutch fork pivot bolt which is 1.5" with a OEM 1.2" flywheel and NOT .96"? I think it should be a 1-3/8".
My success is a tribute to all who took the time to post. Special thanks to Red 71, JustinD, and DZRick.
Melting Slicks
Joined: Dec 1999
Posts: 2,116
Likes: 156
From: Mid West
Cruise-In III Veteran
Three things that I found that help clutch engagement when I did a swap similar to yours are:
1 - A heavy duty pushrod from the Z-bar to the clutch fork. This thing is stiff & strong.
http://www.mr-gasket.com/ProductDeta...minselection=0
2 - Polyurethane motor mounts. If you think about the forces being applied with a mechanical linkage, when you push the pedal down and the rod is forcing against the clutch fork its shoving forward on the engine. Any movement of the engine is wasted motion.
3 - Make sure the pivot ball is correct. I eventually went with an adjustable one so I could fine tune it.
Good luck
1 - A heavy duty pushrod from the Z-bar to the clutch fork. This thing is stiff & strong.
http://www.mr-gasket.com/ProductDeta...minselection=0
2 - Polyurethane motor mounts. If you think about the forces being applied with a mechanical linkage, when you push the pedal down and the rod is forcing against the clutch fork its shoving forward on the engine. Any movement of the engine is wasted motion.
3 - Make sure the pivot ball is correct. I eventually went with an adjustable one so I could fine tune it.
Good luck
Melting Slicks
Joined: Aug 2008
Posts: 2,200
Likes: 3
From: Lehigh county Pennsylvania
This is an OEM Z-bar from my '69 that's been working OK for me for almost 40 years. So no question of its originality.
Note the second, smaller hole is present.
Although I drilled out the oblong, worn hole to 3/8" and inserted a 5/16" steel bushing to facilitate using rod ends linkage, the hole is still on the same centerline...~2.75" above a flat surface.
Last edited by 69 Chevy; Apr 17, 2011 at 08:04 AM.
