Added Factory Brake Booster to 1970 C/10 Now Brake Pedal Sits Low

[cericd]

I have a 1970 C/10 that came with manual 4-wheel drum brakes and 3 OTT transmission. I recently converted the front to disc brakes and added a factory Delco/Moraine 1/2 ton booster from a 1971 C/10 and I can't get the brake pedal to be even with the clutch pedal.

I am using what I believe to be the factory booster brackets and push rod but there doesn't seem to be a way to adjust the brake pedal to the correct position. I've searched but can't find a solution to this issue on the forum. I guess most people don't keep a standard transmission when adding a brake booster. I did see that there are issues with the mounting hole in the brake pedal lever seeming to be in the wrong position for correct linkage geometry.

Were there different brake pedals for trucks with boosters or for trucks with disc brakes?

Someone must have encountered this issue before. Any insight is appreciated.

[Willys_MB]

With the vacuum booster the pedal doesn’t have to sit even with the clutch. I just did this on mine about a year ago. I think the pedal sits somewhere between 1-1.5” lower than before you had a booster. Let me see if I can dig up the picture someone posted.

[Willys_MB]

Here it is:

[Willys_MB]

I used Frank’s system (board member PICKMUP) and followed his instructions and had no issue at all. Measurements all checked out without needing adjustment after install.

[cericd]

Originally Posted by Willys_MB

I used Frank’s system (board member PICKMUP) and followed his instructions and had no issue at all. Measurements all checked out without needing adjustment after install.

Thanks for the info. Would you be able to post a link to the "system" or the instructions you mentioned (or email me a copy of them)? I really want to get this set up correctly. Don't want to fool around and mess my braking system up. Also, just curious, does your truck have a factory clutch?

[pjmoreland]

You should be able to adjust the height of the pedal, as follows:

1) Remove the bolt that attaches the rod to the pedal. In my truck, the steering column gets in the way of removal, so I either have to move the column or detach the brake booster from the firewall so it can be pushed forward

2) Loosen the jam nut on the rod

3) Spin the eyelet on the rod. Thread it out if you want to make your pedal higher. Be sure it is still engaged adequately onto the rod with several turns

Reassemble in the opposite order. You will need to readjust the brake light switch afterward.

[gmc684x4]

I ask have you changed the master cylinder?
Manual and vacuum boost brake systems take a different master cylinder the difference is the depth of the hole in the back where the brake rod comes into contact

[cericd]

This is the master cylinder I got. https://www.autozone.com/brakes-and-...494/715730_0_0

I've heard that there are different master cylinders for booster and non-booster trucks but I didn't see an option to select that when I ordered this re-manufactured unit.

[LockDoc]

-
Read this thread:

http://67-72chevytrucks.com/vboard/s...d.php?t=470102

It might help.

LockDoc

[cericd]

Thanks for the link Leon.

In that thread it says to make sure the bore of the new master looks like the old master cylinder. Unfortunately, my old master cylinder is from a manual drum drum truck. Does anyone know how to determine which master cylinder is correct for a disc/drum truck with a factory 1/2 ton delco moraine booster?

[gmc684x4]

Manual brake master should have a deep pocket
Power boost master has a shallow pocket

[LockDoc]

Originally Posted by cericd

Thanks for the link Leon.

In that thread it says to make sure the bore of the new master looks like the old master cylinder. Unfortunately, my old master cylinder is from a manual drum drum truck. Does anyone know how to determine which master cylinder is correct for a disc/drum truck with a factory 1/2 ton delco moraine booster?

I would say if your old master is the deep one that you would need the shallow one for the disk/drum setup.

LockDoc

[71cadc10]

I went thru exact same thing you describe with my truck. My brake pedal, master, booster, etc. parts were all stock, but the brake pedal was several inches lower than clutch pedal.
I ended up cutting and welding in a 1.5-2" piece of round rod into the threaded pedal rod that goes thru the firewall.
I Don't know why I had to, and I didn't want to do it....but it worked. Still don't know why the lengths didn't work out.
I guess from that earlier diagram, maybe the brake pedal is supposed to be lower than the clutch on a power brake truck?
my issue was it also did not seem to contact the brake light switch and I couldn't adjust the switch up enough to reach it, when it was at that lower setting.

[cericd]

Hey 71cadc10, your solution is the reason I started this thread. It’s the only thing I could think to do to solve the issue but I couldn’t believe that it would be necessary to weld in an extra piece of rod. I thought for sure I was just missing a “correct” part or something. I was hoping I could find another answer here on the forum before cutting into the push rod.

[697498chevy]

Just put a new master cylinder on my 1969 C 10 . Brake pedal's higher than the clutch , probably 4 1/2 to 5 inches from the floor . Can't remember if that's the way it was or not ? Interesting . Thanks !!

[cericd]

Originally Posted by Willys_MB

Here it is:

What manual is this from? I can't find it in my service manual.