Power brake pedal rod question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

gregbr · 04-16-2005, 03:09 AM

I'm adding a power brake booster to my 67 4wd drum/drum setup. The problem is that the adjustable rod from the booster linkage to the pedal is about an inch short (will not adjust out enough). Are there 2 different rods or do I have to change the pedal also?? I did this on my 70 GMC and just welded 2 together to make it longer. Thanks

krue · 04-16-2005, 05:12 AM

I used an adjustable rod on my 70 GMC and it worked fine.

Low69CST · 04-16-2005, 07:06 AM

We've built 2 trucks and had the same problem on both. One truck we had a rod made on the other bought a custom master cylinder/booster that came with a cut to length rod. If you figure it out i'd like to know what the fix is.

HugrOrang71 · 04-16-2005, 03:53 PM

A friend of mine just converted his '69 to power with a late 70's setup and had the same issue. I cut the rod in half and sleeved it with steel pipe. I measured the length to the pedal and built it to be slightly shorter than the actual length so that he would be able to adjust it for fine tuning.

*screamin_c102* · 04-16-2005, 03:57 PM

I had the same issue on Screamin' I just lengthened mine with some tool steel and kept it adjustable , worked out fine

72GMC51 · 04-16-2005, 04:38 PM

I had the same problem on my 72 GMC, also the brake pedal arm does not reach the stop bumper on the front of the dash? I went to a salvage yard and purchased a complete set up (pedal assembly, brackets etc.) from a power brake truck installed it and had the same problem, I ended up with three rods all of them are to short. It seems like the position of the pivot assembly in the truck must be different I have never had a non power brake and power brake truck next to each other to measure but it would be nice to know what the differences is.

JC

gregbr · 04-16-2005, 09:21 PM

I'm glad I'm not the only one. I just welded the one together for my second truck to be done with it. All the threads that talk about converting to power brakes and NOBODY has mentioned this until now?? And it seems most us have had the same problem.

Bob Moore · 04-16-2005, 09:28 PM

What causes the problem? Lets see if we can't figure this out. Is it 3/4T or 1/2T that causes the problem? Drum to disc? Must be something we are using that is wrong vs those that get it right.

**PICKMUP** · 04-16-2005, 10:18 PM

OK, guys...here's what I think the problem is: There is no problem! The pb pedal location is NOT supposed to come back up to the rubber bumper.
Take a look at the pedal location on an original pb truck...the pedal hangs down an inch or so. That is how it is designed. It doesn't need any cutting/welding/adjusting. You just need to make sure you don't extend it so far that it is pre-loading the mc. There should be a little free play so brakes release completely.
Remember, the travel of the pedal into a booster is a lot less than the travel of the pedal directly into a mc.

HugrOrang71 · 04-17-2005, 12:23 AM

I agree with what you're saying about the distance from the pedal to the rubber stop, and the pedal- rod geometry and not extending it so far that it holds pressure on the master cylinder.

In my example, he was using a 78 4wd booster and bracket on a 69 2wd cab. With everything bolted into place, the rod was about 1 1/4" short which meant that it was only about 2" off the floor at the pedal itself. There wasn't enough travel for the brakes to function properly and the brake light switch wasn't contacted. We determined the pedal height by measuring my power setup and some measurements with his manual master cylinder and rod. I also had him compare his pedal ratio to mine. This kept the pedal off the stop, allowed the brake switch to function and most importantly, gave plenty of travel for the brakes to work.

**pjmoreland** · 04-17-2005, 12:38 AM

I had this same problem on a 67 that I installed a power brake booster in from a 70 about 8 years ago. I've always wondered what the cause of this was. I lengthened the shaft too far so that the brake pedal contacted the rubber stop. My brakes wouldn't release completely.

Rod · 04-17-2005, 03:23 AM

Your all using the correct era brake booster and brackets with the adjustable rod to the brake pedal... right?

gregbr · 04-17-2005, 03:04 PM

Yes, I have the same setup in both trucks. I didn't know the pedal was supposed to be an inch away from the rubber stop. I lengthened the rod enough to make it just touch the rubber when adjusted. Oh well, at least I wasn't alone on this one. Thanks guys!!!

04-16-2005, 03:09 AM	#1
gregbr Senoir Member Join Date: Mar 2002 Location: Rock Hill, SC USA Posts: 1,214	Power brake pedal rod question I'm adding a power brake booster to my 67 4wd drum/drum setup. The problem is that the adjustable rod from the booster linkage to the pedal is about an inch short (will not adjust out enough). Are there 2 different rods or do I have to change the pedal also?? I did this on my 70 GMC and just welded 2 together to make it longer. Thanks __________________ 67 Chevy, Small back glass, Factory 4WD, Factory Shortbed, Factory V8, Lifted 4" 70 GMC Sierra Grande, Factory Shortbed, Factory 402/400 turbo, Super Custom Interior. Numbers matching with SPID & Build Sheet. 68K Original Miles. Restored 2010 70 GMC Restoration Pictures http://67-72chevytrucks.com/gallery/...00&ppuser=4424

04-16-2005, 05:12 AM	#2
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,448	I used an adjustable rod on my 70 GMC and it worked fine. __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

04-16-2005, 07:06 AM	#3
Low69CST Registered User Join Date: May 2000 Location: Frankfort, Kentucky, USA Posts: 2,163	We've built 2 trucks and had the same problem on both. One truck we had a rod made on the other bought a custom master cylinder/booster that came with a cut to length rod. If you figure it out i'd like to know what the fix is. __________________ '69 CST Short fleetside Lowered, 400 small block, 700R4, 4 wheel disc brakes, front sway bar & rear camaro sway bar (in progress) '87 V10 4x4 Short Fleetside Quad Suspension and Dual Tanks

04-16-2005, 03:53 PM	#4
HugrOrang71 Bite me, import boy Join Date: Apr 2005 Location: Eagle Point, Oregon Posts: 102	A friend of mine just converted his '69 to power with a late 70's setup and had the same issue. I cut the rod in half and sleeved it with steel pipe. I measured the length to the pedal and built it to be slightly shorter than the actual length so that he would be able to adjust it for fine tuning. __________________ Jason '71 C-10 Deluxe-under construction '69 C20, 396,T400-donor truck, '65 C10 project "Facts are meaningless, You can use facts to prove anything that's even remotely true."

04-16-2005, 03:57 PM	#5
screamin_c102 Account Suspended Join Date: Feb 2005 Location: Yoncalla Oregon Posts: 775	I had the same issue on Screamin' I just lengthened mine with some tool steel and kept it adjustable , worked out fine Last edited by screamin_c102; 04-16-2005 at 04:00 PM.

04-16-2005, 04:38 PM	#6
72GMC51 72GMC51 Join Date: Jul 2004 Location: Minnesota Posts: 233	I had the same problem on my 72 GMC, also the brake pedal arm does not reach the stop bumper on the front of the dash? I went to a salvage yard and purchased a complete set up (pedal assembly, brackets etc.) from a power brake truck installed it and had the same problem, I ended up with three rods all of them are to short. It seems like the position of the pivot assembly in the truck must be different I have never had a non power brake and power brake truck next to each other to measure but it would be nice to know what the differences is. JC __________________ 72 GMC 2wd 1/2 long 350 700r4 A/C PS PB 4:10. Are they ever really finished

04-16-2005, 09:21 PM	#7
gregbr Senoir Member Join Date: Mar 2002 Location: Rock Hill, SC USA Posts: 1,214	I'm glad I'm not the only one. I just welded the one together for my second truck to be done with it. All the threads that talk about converting to power brakes and NOBODY has mentioned this until now?? And it seems most us have had the same problem. __________________ 67 Chevy, Small back glass, Factory 4WD, Factory Shortbed, Factory V8, Lifted 4" 70 GMC Sierra Grande, Factory Shortbed, Factory 402/400 turbo, Super Custom Interior. Numbers matching with SPID & Build Sheet. 68K Original Miles. Restored 2010 70 GMC Restoration Pictures http://67-72chevytrucks.com/gallery/...00&ppuser=4424

04-16-2005, 09:28 PM	#8
Bob Moore Registered User Join Date: Feb 2004 Location: Tacoma WA Posts: 1,365	What causes the problem? Lets see if we can't figure this out. Is it 3/4T or 1/2T that causes the problem? Drum to disc? Must be something we are using that is wrong vs those that get it right. __________________ 67 C-20 LWB, tilt, speed alert, vac, 454, T400 67 C-10 SWB, factory air with more to follow

04-16-2005, 10:18 PM	#9
PICKMUP "Trucks with Class" Join Date: Jul 2000 Location: OLYMPIA, WA, USA Posts: 8,158	The answer...maybe OK, guys...here's what I think the problem is: There is no problem! The pb pedal location is NOT supposed to come back up to the rubber bumper. Take a look at the pedal location on an original pb truck...the pedal hangs down an inch or so. That is how it is designed. It doesn't need any cutting/welding/adjusting. You just need to make sure you don't extend it so far that it is pre-loading the mc. There should be a little free play so brakes release completely. Remember, the travel of the pedal into a booster is a lot less than the travel of the pedal directly into a mc. __________________ Email: frankeham@comcast.net Phone: 360-956-7170

04-17-2005, 12:23 AM	#10
HugrOrang71 Bite me, import boy Join Date: Apr 2005 Location: Eagle Point, Oregon Posts: 102	I agree with what you're saying about the distance from the pedal to the rubber stop, and the pedal- rod geometry and not extending it so far that it holds pressure on the master cylinder. In my example, he was using a 78 4wd booster and bracket on a 69 2wd cab. With everything bolted into place, the rod was about 1 1/4" short which meant that it was only about 2" off the floor at the pedal itself. There wasn't enough travel for the brakes to function properly and the brake light switch wasn't contacted. We determined the pedal height by measuring my power setup and some measurements with his manual master cylinder and rod. I also had him compare his pedal ratio to mine. This kept the pedal off the stop, allowed the brake switch to function and most importantly, gave plenty of travel for the brakes to work. __________________ Jason '71 C-10 Deluxe-under construction '69 C20, 396,T400-donor truck, '65 C10 project "Facts are meaningless, You can use facts to prove anything that's even remotely true."

04-17-2005, 12:38 AM	#11
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,982	I had this same problem on a 67 that I installed a power brake booster in from a 70 about 8 years ago. I've always wondered what the cause of this was. I lengthened the shaft too far so that the brake pedal contacted the rubber stop. My brakes wouldn't release completely.

04-17-2005, 03:23 AM	#12
Rod Join Date: Dec 1999 Location: Eastern - Manitoba Canada, Winnipeg Posts: 4,369	Your all using the correct era brake booster and brackets with the adjustable rod to the brake pedal... right? Attached Images __________________ Senior active founding member. 70 3/4 ton GMC Suburban 4x4 250/4 spd. 71 1/2 ton Suburban Chevy 4x4, 350/350 72 Chev 1 ton tow truck 402BB w/Holmes 440 wrecker on propane 2005 FLSTSCI Harley Springer 85 FXSB Harley Lowrider 72 Triumph 650 Bonneville 5spd "Poor people don't have hobbies" Quote from wife.

04-17-2005, 03:04 PM	#13
gregbr Senoir Member Join Date: Mar 2002 Location: Rock Hill, SC USA Posts: 1,214	Yes, I have the same setup in both trucks. I didn't know the pedal was supposed to be an inch away from the rubber stop. I lengthened the rod enough to make it just touch the rubber when adjusted. Oh well, at least I wasn't alone on this one. Thanks guys!!! __________________ 67 Chevy, Small back glass, Factory 4WD, Factory Shortbed, Factory V8, Lifted 4" 70 GMC Sierra Grande, Factory Shortbed, Factory 402/400 turbo, Super Custom Interior. Numbers matching with SPID & Build Sheet. 68K Original Miles. Restored 2010 70 GMC Restoration Pictures http://67-72chevytrucks.com/gallery/...00&ppuser=4424



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