The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1967 - 1972 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 04-15-2014, 05:20 PM   #1
eric8
Registered User
 
Join Date: May 2013
Location: Utopia
Posts: 215
Adding a clutch pedal

I have always read that on 67-72's, "autos and manuals used the exact same pedal box. GM just slid a clutch pedal on the end of the manuals." Well I now have located a manual transmission complete pedal box and pedal assembly, and they indeed appear to have a small difference.

If you'll reference the attached pic, I am pointing to part of the pedal box that is not part of the stamping on the original auto pedal box on my 72 C10. This stamping is where the very heavy clutch return spring attaches. Why are there two return springs?

I'm doing a T56 hydraulic clutch swap. Do I need both return springs? I'd like to keep the original pedal box in place and just add on the clutch pedal if possible.
Attached Images
 
eric8 is offline   Reply With Quote
Old 04-15-2014, 07:19 PM   #2
eric8
Registered User
 
Join Date: May 2013
Location: Utopia
Posts: 215
Re: Adding a clutch pedal

This factory diagram only shows a light return spring at the top of the pedal arm. Any ideas? M
Attached Images
 
eric8 is offline   Reply With Quote
Old 04-15-2014, 07:37 PM   #3
imjeff
Registered User
 
imjeff's Avatar
 
Join Date: Feb 2008
Location: Tacoma Washington
Posts: 890
Re: Adding a clutch pedal

Looks like a PO probably added a spring to get the clutch pedal to fully return. Sometimes, depending on the adjustment, they can hang down a little. The hydraulic set up should only require one spring.
__________________
I know a guy who's addicted to brake fluid. He says he can stop any time.
72 K10 396
75 Cj5 MPI 350 Chev
67 Chevelle 396, 4 speed
74 FXE
08 Tahoe
imjeff is offline   Reply With Quote
Old 04-15-2014, 08:09 PM   #4
eric8
Registered User
 
Join Date: May 2013
Location: Utopia
Posts: 215
Re: Adding a clutch pedal

Interesting idea Jeff but I'm almost confident this looks to be a factory setup. If you look in the diagram above, the item labeled "production brake pedal support" looks like my auto setup. If you look at the shape of the manual setup I have, you can see it is shaped much different and extends over toward the driver's side to the clutch pedal.
Attached Images
 
eric8 is offline   Reply With Quote
Old 04-15-2014, 08:27 PM   #5
imjeff
Registered User
 
imjeff's Avatar
 
Join Date: Feb 2008
Location: Tacoma Washington
Posts: 890
Re: Adding a clutch pedal

I believe you're right after looking at the diagram and pics again. I will keep pondering...maybe my old mind will recall a useful fact! Lol! That spring looks a lot like the generic ones they used to sell in parts stores. There are a couple I've launched in about the same orbit as Sputnik.
__________________
I know a guy who's addicted to brake fluid. He says he can stop any time.
72 K10 396
75 Cj5 MPI 350 Chev
67 Chevelle 396, 4 speed
74 FXE
08 Tahoe
imjeff is offline   Reply With Quote
Old 04-15-2014, 08:43 PM   #6
eric8
Registered User
 
Join Date: May 2013
Location: Utopia
Posts: 215
Re: Adding a clutch pedal

It is much much larger than it looks in the pics. Super heavy spring. After playing around with it and pushing the pedal through its range of travel, the big spring appears to be the exact opposite of a return spring. Rather, it feels like it is assisting the pedal to go to the floor once it gets through the first 25% of its travel. Maybe it was used on C20s with super heavy duty clutch setups, so the pedal effort wouldn't seem so high? You'd still think they would show the spring in the parts breakdowns or assembly manuals if that were the case though.
eric8 is offline   Reply With Quote
Old 04-15-2014, 08:50 PM   #7
ray_mcavoy
Registered User
 
Join Date: Nov 2009
Location: Sherman, ME
Posts: 2,350
Re: Adding a clutch pedal

Quote:
Originally Posted by eric8 View Post
After playing around with it and pushing the pedal through its range of travel, the big spring appears to be the exact opposite of a return spring. Rather, it feels like it is assisting the pedal to go to the floor once it gets through the first 25% of its travel.
That's often called an "over center" spring and does exactly as you described. It assists in pushing the pedal down once the pedal travel goes beyond the center pivot point of the spring.

Quote:
Originally Posted by eric8 View Post
Maybe it was used on C20s with super heavy duty clutch setups, so the pedal effort wouldn't seem so high? You'd still think they would show the spring in the parts breakdowns or assembly manuals if that were the case though.
This diagram is from the assembly manual (sorry, scanner clipped off the LH side a bit but I think you can still read most of it). Looks like it was used in medium duty trucks:

ray_mcavoy is offline   Reply With Quote
Old 04-15-2014, 09:01 PM   #8
eric8
Registered User
 
Join Date: May 2013
Location: Utopia
Posts: 215
Re: Adding a clutch pedal

You are the man Ray! I don't know how I missed that in the assembly manual I have (actually, I do know how.....as I'm sure I don't need to tell you how badly disorganized that thing is. It is seriously in need of some type of index or table of contents). Thank you for putting the mystery to rest!
eric8 is offline   Reply With Quote
Old 04-15-2014, 09:08 PM   #9
imjeff
Registered User
 
imjeff's Avatar
 
Join Date: Feb 2008
Location: Tacoma Washington
Posts: 890
Re: Adding a clutch pedal

Thank you! I started out looking at the wrong spring, but now the mystery is solved!
__________________
I know a guy who's addicted to brake fluid. He says he can stop any time.
72 K10 396
75 Cj5 MPI 350 Chev
67 Chevelle 396, 4 speed
74 FXE
08 Tahoe
imjeff is offline   Reply With Quote
Old 04-15-2014, 09:37 PM   #10
ray_mcavoy
Registered User
 
Join Date: Nov 2009
Location: Sherman, ME
Posts: 2,350
Re: Adding a clutch pedal

Quote:
Originally Posted by eric8 View Post
You are the man Ray! I don't know how I missed that in the assembly manual I have (actually, I do know how.....as I'm sure I don't need to tell you how badly disorganized that thing is. It is seriously in need of some type of index or table of contents). Thank you for putting the mystery to rest!
You're welcome!

Yeah, I have a bunch of different assembly manuals for my various projects and I have to say the 67-72 truck one is one of the worst in terms of organization. Mine is full of pieces of paper I've used to bookmark certain pages but it still takes a while to find stuff in there. I've also noticed that it doesn't show the original GM part numbers like a lot of the other assembly manuals. Oh well, at least it's better than not having anything available ... as is the case for some of the cars I own.
ray_mcavoy is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 03:32 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright 1997-2022 67-72chevytrucks.com