'72 C20 350/SM465 - Pedal push rod lever adjustment

[johnscab]

Hi. Looking for some help on a clutch setup on this C20 i bought. Its a factory V8 with an SM-465. The kid before me got the clutch done and it was having trouble shifting. There was CRAZY adjustment on the lower rod with washer shims and the adjustment nuts were at their maximum. I pulled the motor to rebuild it. Upon inspection, I found the fingers of the new pressure plate were uneven, which I thought was the issue since there was not an even disengagement of the clutch... however, I bought a new RAM setup and installed it. Same adjustment. I removed the upper linkage and it was bent, so i straightened it.... however that didn't solve the issue. I read a unch of threads and I think that the pedal pus rod lever on the pedal assembly may be wrong. The pedal all the way up, the lever is pointing directly back at the driver. Is this correct? Help. Please.

[geezer#99]

Pics!!
We need pics of your z-bar and linkage by the motor and back to the tranny.

[johnscab]

Hi. I will get more pictures. in the mean time, here is a video of the mechanics.

https://drive.google.com/file/d/0BzP...ew?usp=sharing

here is a picture of the lever on the clutch pedal assembly. the firewall is to the right of the picture and the lever is pointing to the left and slightly up. This would be pointing at the driver.

https://drive.google.com/open?id=0Bz...mFSSXAyQ2hjMU0

Thanks!!

[geezer#99]

Your z-bar looks ok but the pushrod from under the dash is suspect.
Sounds like it hits the firewall metal in the opening. You can hear interference now but when you get it running you'll get some body and frame movement that could make it worse.
I had one like that once. The rod hung up on the sheetmetal causing a chatter due to not having a clean release.
You might need to do a little bending or sheetmetal moving. Sheetmetal is easier as the rod is likely hardened and won't bend easily.

And OOOPS!!!
Welcome to the forum!!

[johnscab]

Thanks for writing back and thanks for the welcome.

The upper rod was bent. Whoever had done the clutch job before really buggered the whole thing up. The upper rod had bent so badly that it tore the firewall... I had to bend the upper rod back and weld the firewall back up. There stil is just not enough throw to move the fingers on the pressure plate. The very end of the movement in the video is when the pressure plate starts to disengage.

Still though, the question is to the position of that lever on the clutch assembly... mechanically speaking, this is not moving linkage very far at all. Can this be adjusted? If it can be, then I am assuming it will look different on each application...

[geezer#99]

A link from LMC.
http://www.lmctruck.com/icatalog/cb/full.aspx?Page=144

Looks like you need a new rod (2) and nut(3) and then you can make a better adjustment.
You might also need to put the nut (32) into the inner hole on the fork to give you more movement on the tob.

[johnscab]

The 2 parts you outlined are the in fine condition... though I don't know if the rod that I have is correct. Do you know where I can find dimensions for that rod so that I can verify things like length? Mine seems to short... which only points to the whole system being short by a couple inches...

Still, any idea on the clutch assembly lever position?

[geezer#99]

THe rods I've seen usually have about 3 inches of exposed thread on the end to help with adjustment. I don't know the correct length.
When I set up my linkages I always set the tob against the fingers, adjusted the rod to hold it there, then backed off the rod adjustment just enough to give about 1/4 inch of freeplay for the tob on the fingers.

You might want to set it that way with the nut in the inner hole on the fork.

It's possible your fork is not right too. They made all shapes of them.
Look here.
http://www.4speedconversions.com/gm-forks

Also, the pivot ball for the fork is adjustable too but the tranny has to come out to set it.

[johnscab]

Geezer#99. I want to thank you again for your attention and help!! While I am not opposed to replacing every part, something still just does not fit... if I replace everything and don't really know what the issue was, it will still burn me inside.... so,

Here is some more information.

Clutch fork: straight and cast iron. Original from the truck.
Pivot ball on the bellhousing: fine condition. Regreased prior to engine install.
Pushrod nut: looks good. no excessive wear.
Push rod: straight, threads are fine, no excessive wear.
Linkage Swivel: working order. Swivel pivot area is slightly worn.
Linkage swivel nuts: fine condition
Z bar: good condition. no excessive wear.
Zbar engine pivot: normal wear.
Zbar frame pivot: cleaned up the threads for easy reinstall, normal wear.
Upper clutch rod: normal wear on the pivot points. scored on the side from the firewall. Was bent. I bent it back using a vice and small increments. I believe it is still slightly bent. probably need to confirm the length of a new or used original.


The pressure plate and throwout bearing are new... meaning that the original pressure plate was probably a flat finger plate with a long throwout bearing... The new is a diaphram type with fingers protruding outwards towards the throwout bearing.

I have the setup and measured the total distance from back of the flywheel to the end of the throwout bearing and the different was a 1/4"...

After reading numerous threads, I thought it could be the throwout bearing, but after bench-verifying and then installing and mating the engine to the trans, the clutch fork is only about 5-10 degrees towards the back of the truck when seating the throwout bearing to the pressureplate fingers.

Need to confirm for anyway to weigh in on:

1. Dimensions of the upper clutch rod. how long? and which end attaches to which location? there is one section that is pressed flat. This was connected to the Zbar on my application.

2. After reviewing the shop manual, it shows the pedal push rod lever pointing straight back... I will verify if this is adjustable, but am looking for input as to what other applications look like (for those of you who have manual transmissions installed on your trucks). Is it pointing straight back when the pedal is in the normal position? is it pointing down?

Thanks again all for the insight!!

Cheers, John

[LockDoc]

-
This is from the '67-'72 GM Assembly Manual.

LockDoc

[Wrenchbender Ret]

That lever under the dash just doesn't look right.

[johnscab]

Originally Posted by LockDoc

-
This is from the '67-'72 GM Assembly Manual.

LockDoc

The picture of my pedal set up looks more like what is cut off in the picture. I have the large spring attached down the pedal.

[johnscab]

Originally Posted by Wrenchbender Ret

That lever under the dash just doesn't look right.

I verified that the lever has part grooves and part flat area. My daughter was screaming so I couldn't work to remove the lever and inspect exactly what the end of the shaft and lever look like once removed...

[johnscab]

Originally Posted by LockDoc

-
This is from the '67-'72 GM Assembly Manual.

LockDoc

It looks more like the lower picture that is attached here. Though the lever position looks like the top picture...

[1972k5blazer]

here is a rod out of a 72 v8 4 speed 4x4 not sure if this helps you on not

[johnscab]

Originally Posted by 1972k5blazer

Attachment 1499788 here is a rod out of a 72 v8 4 speed 4x4 not sure if this helps you on not

You are awesome!!!! Thanks!

[johnscab]

So I have had some time to look into the issues and I think I may have found the problem.

1. THe lever position pointing straight back appears to be the right position.

2. I confirmed that the upper clutch rod that I have is 19 1/2" like the other one that was posted in this feed by 1972k5blazer.

3. I was reading two other threads:
http://67-72chevytrucks.com/vboard/s...d.php?t=667853
http://67-72chevytrucks.com/vboard/s...d.php?t=627068

Basically, there is a longer lower rod. Based on some information I found, the longer rod is for teh 6 cylinder applications or possibly 4x4, which I don't quite understand why, but based on the different positions of the engines, the variations of trannys, poswer vs manual everything, I have decided that I just don't care at this point.

4. I measured my lower rod and it was total length of 10 1/4"

Next:

I decided to extend my lower rod, because I just wasn't disengaging the clutch until the end of the throw of my pedal... based on my measurements, I needed about 2 more inches, based on the information in one of those feeds, he said the other rod was about 4" longer. So i decided to add 3" so that I had ample adjustment.

This ultimately ended up being too long. but i was able to get the desired action from whole system. I will probably remove an inch from the lower rod because I think it may interfere with the exhaust, but we will see.

So my next questions are:

1. does anyone have a 4x4 or stick cylinder lower rod that they can confimr the measurement?

2. Which position on the clutch fork should the rod be connected to? The outer hole seems to have better geometry, but the inner hole is where the rod was attached when I got the truck.

Thanks!!

John