Brakes & service manuals

[Andy4639]

I have 3 service manuals and one shop manual for the 67-72 Chevy trucks that I refer to often when working on the 71 C-10 and the 67 C-20 Ramp truck.
Nothing in any of them show 2 holes on the brake pedals are mention them with different holes for the brakes weather they are manual are power doesn't even talk about that. Everything shows the same mounting points and how to adjust for each.
Another note they don't mention if the brake pedal should are shouldn't rest on the brake stops on the top of the bracket. I'm talking about the rubber stops in the bracket under the dash. All of them talk about free play and how to adjust them but nothing on the stops.
All the manuals except the 71 manual state the pedal off the floor measurement though. Why???? I have no idea why.
First is the 69 manual.

[Andy4639]

Here is the GMC 1500 thru 3500 series. It's pretty much like the 69.
Neither mention another hole for the push rod.

[Andy4639]

Here is the 71 manual and it has the least info on the pedal.
Again no mentioning of a standard hole and power assist hole on the brake pedal at all. Just how much free play to have.
So can some one explain.
I've worked on these trucks 35+ years and have never seen a brake pedal with 2 holes in it ever. Both of mine have 1 hole. My 71 C 10 was factory power brakes. My 67 Ramp was manual drums when I bought it. It now has power brakes and I used the same hole in the brake pedal.

[Mike C]

I don't believe there are two. They change pedal ratio with the offset linkage that locates the booster up. Which is why you cannot use a square body power booster setup on these trucks and have it just bolt on

[firedemon]

I am so glad you posted this I have been trying to figure this out for some time . if I adjust the pedal to the measurement given for floor clearance it is nowhere near the rest stop at the top . I also worry that that 1.25 with power wont have enough pedal if I blow a front line seems like id need new shorts if the pedal dropped being that close to the floor . mine had manual drum and the pedal was at the rest stop then engaged about half way down . with the disk conversion and power booster if I adjust so its at the rest stop it starts to engage way high maybe an inch from the stop and way fast almost kiss the windshield if im not paying attention , and not a lot of thread engagement in the rod

[Andy4639]

Your welcome sir,
There has ben a lot of talk about how to adjust and how to drill another hole. I have been fighting this as well and decided to look and see how the manual's say to do it. There are people on here that state things and everyone thinks they are the only ones who know. I have never seen a brake pedal with 2 holes ever and I have been working on these trucks for over 40 years now.

[firedemon]

I have never seen 2 holes either and my rod is straight with the factory hole seems if I put a hole it would be at a angle that dosent seem right . I guess what we would need is some detailed pics of a 71-72 factory disk setup of the pedal in its relaxed state distance from the rest at the top and its distance to the floor . when fully pressed the distance to the floor

[tdangle]

Yesterday I adjusted the pedal height higher and it didn't change. the free play. What creates the free play? Also my pedal arm only has 1 hole. And then there is that offset linkage on the outer firewall that connects to the booster unit. I wonder if this is the ratio I hear about when using power brakes vs manual. Does the manual system have that offset linkage??

[Steeveedee]

Like Jocko mentioned, the arm in his '66 truck had two holes. I suspect that the holes are maybe in a different place for manual Vs power, and it wouldn't surprise me if there were two part numbers. I've never seen an arm with two holes, but then in my mechanic days I didn't go changing parts all over, I repaired the vehicle and sent it on its way. I did switch over a '69 Nova from manual drum to power disc back in the '80s, but everything bolted right up.

[Andy4639]

My 71 C 10 is factory disc/drum but I have installed rear disc on it now. All the parts are still in tact from the factory except rear brakes. The ramp truck was manual drums up until I added the booster. I used the same mounting hole for it on the brake pedal.

[firedemon]

did you have to move the pedal adjustment to account for the rear disk ?

[Andy4639]

Originally Posted by firedemon

did you have to move the pedal adjustment to account for the rear disk ?

I have adjusted the rod to the pedal to get it where I like it.

[tdangle]

Andy,
I think I found part of the answer. I went thru the assembly manual and from what I see the brake pedal is the same (maybe much earlier ones had 2 holes) The difference is in the bracket assembly. Looks like for the manual brake setup the rod from the brake pedal goes straight to the master cylinder that is bolted directly to the firewall. If a booster is present then it looks like (at least for 10-30 series) the rod from the pedal goes to the center of a lever that pivots at the bottom of the bracket and the booster rod connects to the top of the level. I can only assume that this setup would possibly reduce the pressure applied to the booster.

[firedemon]

Originally Posted by Andy4639

I have adjusted the rod to the pedal to get it where I like it.

that's what I did too the manual is clear as mud sometimes

[Andy4639]

Originally Posted by firedemon

that's what I did too the manual is clear as mud sometimes

The shop manuals are pretty straight forward. The assembly manual is tough to figure out in my opinion. The drawings are less than what I was hoping for as well as the tips and write ups.