The Stovebolt Site Forums The Shop Area Driveline Brake pedal height.

On my 47 3600 with the OEM master cylinder under the floor and SM420 transmission that came in the truck when I bought it. Both arms on the firewall parallel to the floorboard. New rubber bumpers on the arms. The brake pedal is about 2 inches higher that the clutch pedal. It seems high to me. I was thinking about shortening the pedal to be more level with the clutch pedal. I have more than 8” of pedal above the floor. The clutch pedal is 8.5” long the brake pedal is 11” long. The distance on the connecting arms to the floorboard is not equal between them so they can’t be the same length I get that. But the pedals can be closer to height if I choose to alter the brake pedal. I am building this truck to be better driving that it was when I bought it. I have hard brake pedal at 3” of pedal travel. What would be your guys opinion. Does anyone have pictures of their clutch and brake pedals?

The brake pedal is probably in the correct position. Your clutch pedal is probably too low for some reason.

Section 5-8 of the shop manual details pedal adjustment.

It says it should be adjusted so that the top edge of the brake pedal arm (under the firewall) is 13/16" from the toe pan/firewall.

The brake pedal on my truck is about 1/2" higher than the clutch pedal. Both the clutch and master cylinder are new.

I have cut off the foot part of the pedal & removed enough of the shaft to get them even & welded the pad back on. I have done this to several trucks & it makes it much more pleasurable to drive.
I assume this is the second series 1947 model. Like the 48 up AD models.

George

The clutch pedal arm has new rubber bumper on it. It sets the gap on the arm to the floorboard, I assume to the right gap, I'll check. I adjusted the clutch free play to give my throw out bearing the proper clearance. The brake arm activates the original OEM brake light switch. I put a rubber bumper on the brake arm to not over travel the switch and smash it against the floorboard. If I did not, the switch lever would be the only thing stopping the brake arm, and it would be even higher. There is a little difference between the two arms, one is angled, and one is straight. The pedal shafts are 2.5" different in length. My master is the original rebuilt, my clutch is the original 10 3/4" pressure plate but a new disc and throw out bearing.

The only downside to lowering the height of the pedal above the floorboard is the corresponding decrease in the stroke of the master cylinder piston. Being very conscientious about brake adjustment (or converting to self-adjusters) will keep the pedal travel to a minimum. It's not difficult to convert any Bendix drum brake system to be self adjusting.
Jerry

If your brake arm is smashing your brake light switch lever against the floorboard, you likely have a cab-to-frame alignment issue which you need to investigate. There is an internal stop inside of the master cylinder which dictates the position of the piston at rest (no brakes applied). There is an adjustable pushrod which when adjusted, dictates the distance between the firewall and the brake arm. That bumper on your brake arm may be adversely altering the action of the piston inside of the master cylinder.

I will investigate the brake push rod adjustment. I am in the process of reassembly. My cab support is fine, I put new rubber pads in already. I have not finalized the adjustments. I installed the brake light switch and put a ohm meter on it to know where it activates. That is where the arm should rest, just behind where the light goes out. I will adjust the brake push rod to the master cylinder so it is at rest and the switch is off. Thanks.

You should finalize the cab adjustment before you adjust anything brake related.
The master cylinder is mounted to the frame. If the cab is not in the correct position on the frame, you will run into issues like you are having.
Adjustment of the pushrod involves obtaining a specific distance between the brake lever and the toeboard (you will need to look that up in the Chevrolet Truck Repair Manual). If your cab is not positioned correctly, fore and aft, up and down, and side to side, that gap between the brake lever and the toeboard will be meaningless and may adversely affect the manner in which the master cylinder functions.

"If it ain't broke... Don't fix it."
Get the brake light switch working properly and enjoy the ride.

Or you you can do what Jethro suggests. Brakes, schmakes. Everyone else on the road just needs to pay closer attention to other drivers, right?

Will do. I still wonder why the brake pedal shaft though the floor is 3” longer than the clutch pedal shaft. Both arms out on the firewall are not that far out of sink with each other. I will finish my adjusting and checking things this week.