What is this brake thing? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

GoranL · 03-10-2010, 04:03 PM

Hi all!

I´ve been working on my brakes on my -68 swb stepper, and need som help. It originally had a l6 and manual drum brakes, it´s been updated somewhere along the line and now has a 350+th350 and the brakes are disks up front and stock rear drums with hydroboost power assist.

Since I bought the truck last summer I had brake problems, because the rears were locking up before the fronts and I had no real power assist. So I have overhauled the calipers, main cylinder and replaced the wheel cylinders since one of them was leaking, and also one of the wheel seals were leaking, and that´s also been taken care of.

Anyway, today when I was lying under the truck I discovered this thing, connected to the rear brake line. It sits on the frame, on the passenger side just in front of the rear spring. What does it do? Do I need it? Does it hurt anything? It is not connected to anything, electrically or mechanicaly, I can´t understand what it´s supposed to do?

ricks71pu · 03-10-2010, 04:15 PM

a "hill holder" of sorts? my old studebakers had them. interesting.

Keith Seymore · 03-10-2010, 05:06 PM

Just guessing, but I wonder if it's some kind of (adjustable) proportioning valve.

K

Arizona oldguy · 03-10-2010, 05:16 PM

I with adjustable proportioning valve, I saw one on a jeep my buddy was building

**michael bustamante** · 03-10-2010, 05:17 PM

it sounds more like when the brakes were modded, the old prop valve for drum drum was still used, you might have to swith the prop valve for a disk drum run so the rears wont lock up so quickly,
as for the pic, Ive never see one of those before on our trucks. Hmmm

johnechi · 03-11-2010, 04:02 AM

That is a brake proportioning valve. Not stock. Since you are running front disc and rear drum I would remove the that unit and either put in a union or run a new hard line altogether. I assume you are running a disc/drum brake master cylinder.

ERASER5 · 03-11-2010, 04:40 AM

What he said.

GoranL · 03-11-2010, 06:16 AM

Thanks for the replies!
The prop valve is for disks front and drums rear, and the master cylinder is also for disks/drums.
I think I will go ahead and just remove the thing.

03-10-2010, 04:03 PM	#1
GoranL Registered User Join Date: Aug 2009 Location: Sweden Posts: 3	What is this brake thing? Hi all! I´ve been working on my brakes on my -68 swb stepper, and need som help. It originally had a l6 and manual drum brakes, it´s been updated somewhere along the line and now has a 350+th350 and the brakes are disks up front and stock rear drums with hydroboost power assist. Since I bought the truck last summer I had brake problems, because the rears were locking up before the fronts and I had no real power assist. So I have overhauled the calipers, main cylinder and replaced the wheel cylinders since one of them was leaking, and also one of the wheel seals were leaking, and that´s also been taken care of. Anyway, today when I was lying under the truck I discovered this thing, connected to the rear brake line. It sits on the frame, on the passenger side just in front of the rear spring. What does it do? Do I need it? Does it hurt anything? It is not connected to anything, electrically or mechanicaly, I can´t understand what it´s supposed to do? Attached Images

03-10-2010, 04:15 PM	#2
ricks71pu Registered User Join Date: Feb 2010 Location: salem oregon Posts: 225	Re: What is this brake thing? a "hill holder" of sorts? my old studebakers had them. interesting.

03-10-2010, 05:06 PM	#3
Keith Seymore Registered User Join Date: May 2009 Location: Motor City Posts: 9,213	Re: What is this brake thing? Just guessing, but I wonder if it's some kind of (adjustable) proportioning valve. K __________________ Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/

03-10-2010, 05:16 PM	#4
Arizona oldguy Registered User Join Date: Jan 2009 Location: Queen Creek Arizona Posts: 56	Re: What is this brake thing? I with adjustable proportioning valve, I saw one on a jeep my buddy was building

03-10-2010, 05:17 PM	#5
michael bustamante Senior Member Join Date: Sep 2007 Location: Albuquerque NM Posts: 7,855	Re: What is this brake thing? it sounds more like when the brakes were modded, the old prop valve for drum drum was still used, you might have to swith the prop valve for a disk drum run so the rears wont lock up so quickly, as for the pic, Ive never see one of those before on our trucks. Hmmm __________________ 1967custom

03-11-2010, 04:02 AM	#6
johnechi Registered User Join Date: Jun 2009 Location: Hesperia, CA Posts: 159	Re: What is this brake thing? That is a brake proportioning valve. Not stock. Since you are running front disc and rear drum I would remove the that unit and either put in a union or run a new hard line altogether. I assume you are running a disc/drum brake master cylinder.

03-11-2010, 04:40 AM	#7
ERASER5 Registered User Join Date: Jun 2006 Location: Indiana Posts: 4,859	Re: What is this brake thing? What he said. __________________ '70 GMC C1500 LWB Power disc brakes. WooHoo! Posi 6 Lug Dana 60

03-11-2010, 06:16 AM	#8
GoranL Registered User Join Date: Aug 2009 Location: Sweden Posts: 3	Re: What is this brake thing? Thanks for the replies! The prop valve is for disks front and drums rear, and the master cylinder is also for disks/drums. I think I will go ahead and just remove the thing.

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