Proportioning Valve??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

HotRod929 · 02-17-2003, 12:03 PM

I have drum brakes all around and I also have a proportioning valve right after my m/c. I was wondering weather I need this or not? I dont think it came from the factory like this but I could be wrong. Please let me know. Also can I replace it with an adjustable proportioning valve? If so where can I get one and what kind should I get. THanks

HotRod

vycc · 02-17-2003, 12:13 PM

yes you need this.... it determines the amount of presure to give the front/back brakes......keep it on there

PS - if you have to replace it you can get them anywhere, they're for any chev.

XXL · 02-17-2003, 12:42 PM

This may simply be a distribution block with pressure sender (the connector for the brown wire on the bottom). That is what should have come on a drum/drum setup.

Kenneth

spinning wheels · 02-17-2003, 02:02 PM

If you replace it make sure its for a drum to drum setup. The disk to drum proportioning valves are different as are the disk to disk valves. The adjustable valves are usually used on race cars and are adjusted according to what track they are racing at. I don't think I would run one on a street vehicle. Thats just my opinion.

Bruce68SB · 02-17-2003, 05:35 PM

That is not a proportioning valve. Although it resembles one. It is a "brake warning light switch. All drum brake trucks came with them. If you loose pressure in one side of your brake system, (either front or back) a piston inside it will move to one side (off center) and make an electrical connection for that wire you see hooked to it. That will light a dummy light on your dash. So kep it, you need it.
By the way, I would like to make a suggestion. Next time you ask a technical question like this, you might give some details about your truck, (year, series, engine, trans, ect.)
--Regards, BA

HotRod929 · 02-17-2003, 06:31 PM

Bruce68SB - Thanks for the info. all the details about my truck are at the bottom of all my posts.

HotRod

wxman1 · 02-17-2003, 06:32 PM

Bruce68SB is on the mark here.

Quote from 1969 Chevy Service Manual:
"Note: The brake pressure differential warning switch
is a non-adjustable, non-serviceable valve. If defective
it must be replaced."

"CA-KA-PA10-20, CA-PA-30,GA10-20 and SA-40-50 models
are equipped with a brake pipe distribution and switch assembly
(Fig 9). The front and rear hydraulic brake lines are routed from
the main cylinder, through the switch assembly, to the front and
rear brakes. The switch is wired electrically to the brake alarm
indicator light on the instrument panel. In the event of fluid loss
in either the front or rear brake system, the indicator on the
instrument panel will illuminate red when brake pedal is
depressed"

Image is attached.

So now having quoted the manual on this feature...I ask this
question. I have a custom dash. There is NO brake warning
light. So what good is this brake warning switch in MY case?

Jim M.
Mt Juliet, TN

spinning wheels · 02-17-2003, 08:12 PM

that is the proportioning valve. you still need regardless of the warning light.
Hey Hotrod, could you give a rundown on how you wired your Sun tach. I picked one up at a swapmeet. I'm stumped on some of the wires. This tach has six wires.
Thanks

Bruce68SB · 02-26-2003, 12:28 AM

:p Ok- You got me.
If you have drum brakes all the way around, and no warning light on your dash,. you can chuck the brake warning light switch.

Drum brake trucks do not need a proportioning valve.
This is because the extra braking power the front brakes need is accomplished
by another method. On drum brake trucks, the front wheel [brake] cylinder pistons are larger diameter than the ones on the rear brakes.
--Regards, Bruce

HotRod929 · 02-26-2003, 02:11 AM

Bruce68SB - I do have a warning light on my dash. I think that the thing circled in the pic is just a brake pressure warning light swich.

02-17-2003, 12:03 PM	#1
HotRod929 Registered User Join Date: Mar 2002 Location: Bondurant, IA but in Worcester, MA for school Posts: 767	Proportioning Valve??? I have drum brakes all around and I also have a proportioning valve right after my m/c. I was wondering weather I need this or not? I dont think it came from the factory like this but I could be wrong. Please let me know. Also can I replace it with an adjustable proportioning valve? If so where can I get one and what kind should I get. THanks HotRod Attached Images __________________ 1970 Chevy C-20 350 V-8 Turbo 350 w/ shift kit Dana 60 w/ 4.10 gears AND Powr-Loc POSI New Additions: Summit Headers 135amp alternator Proform HEI Edelbrock 1406 600cfm carb Sunpro Tach Powr-Loc POSI Edelbrock Performer RPM Intake MSD 6A Ignition Box AIM: HotRod929 Visit My Site: http://1970chevy.netfirms.com/

02-17-2003, 12:13 PM	#2
vycc Registered User Join Date: Feb 2003 Location: Victoria,BC Canada Posts: 125	yes you need this.... it determines the amount of presure to give the front/back brakes......keep it on there PS - if you have to replace it you can get them anywhere, they're for any chev. __________________ 1981 GMC Sierra 1/2 Ton SWB 4X4 Last edited by vycc; 02-17-2003 at 12:16 PM.

02-17-2003, 12:42 PM	#3
XXL Señor Member Join Date: May 2002 Location: Edge of the world Posts: 5,367	This may simply be a distribution block with pressure sender (the connector for the brown wire on the bottom). That is what should have come on a drum/drum setup. Kenneth __________________ Craigslist \| ebay \| Engrishtees \| www.myattitudesucks.com \| Follow me on Twitter

02-17-2003, 02:02 PM	#4
spinning wheels Registered User Join Date: Sep 2001 Location: Hacienda Heights, California USA Posts: 474	If you replace it make sure its for a drum to drum setup. The disk to drum proportioning valves are different as are the disk to disk valves. The adjustable valves are usually used on race cars and are adjusted according to what track they are racing at. I don't think I would run one on a street vehicle. Thats just my opinion. __________________ '72 GMC custom camper 350/350

02-17-2003, 06:31 PM	#6
HotRod929 Registered User Join Date: Mar 2002 Location: Bondurant, IA but in Worcester, MA for school Posts: 767	Bruce68SB - Thanks for the info. all the details about my truck are at the bottom of all my posts. HotRod __________________ 1970 Chevy C-20 350 V-8 Turbo 350 w/ shift kit Dana 60 w/ 4.10 gears AND Powr-Loc POSI New Additions: Summit Headers 135amp alternator Proform HEI Edelbrock 1406 600cfm carb Sunpro Tach Powr-Loc POSI Edelbrock Performer RPM Intake MSD 6A Ignition Box AIM: HotRod929 Visit My Site: http://1970chevy.netfirms.com/

02-17-2003, 05:35 PM	#5
Bruce68SB Registered User Join Date: Jan 2001 Location: Pomona, CA, USA Posts: 90	That is not a proportioning valve. Although it resembles one. It is a "brake warning light switch. All drum brake trucks came with them. If you loose pressure in one side of your brake system, (either front or back) a piston inside it will move to one side (off center) and make an electrical connection for that wire you see hooked to it. That will light a dummy light on your dash. So kep it, you need it. By the way, I would like to make a suggestion. Next time you ask a technical question like this, you might give some details about your truck, (year, series, engine, trans, ect.) --Regards, BA

02-17-2003, 06:32 PM	#7
wxman1 Senior Member Join Date: May 2002 Location: mt juliet, tennessee, usa Posts: 237	Bruce68SB is on the mark here. Quote from 1969 Chevy Service Manual: "Note: The brake pressure differential warning switch is a non-adjustable, non-serviceable valve. If defective it must be replaced." "CA-KA-PA10-20, CA-PA-30,GA10-20 and SA-40-50 models are equipped with a brake pipe distribution and switch assembly (Fig 9). The front and rear hydraulic brake lines are routed from the main cylinder, through the switch assembly, to the front and rear brakes. The switch is wired electrically to the brake alarm indicator light on the instrument panel. In the event of fluid loss in either the front or rear brake system, the indicator on the instrument panel will illuminate red when brake pedal is depressed" Image is attached. So now having quoted the manual on this feature...I ask this question. I have a custom dash. There is NO brake warning light. So what good is this brake warning switch in MY case? Jim M. Mt Juliet, TN

02-17-2003, 08:12 PM	#8
spinning wheels Registered User Join Date: Sep 2001 Location: Hacienda Heights, California USA Posts: 474	that is the proportioning valve. you still need regardless of the warning light. Hey Hotrod, could you give a rundown on how you wired your Sun tach. I picked one up at a swapmeet. I'm stumped on some of the wires. This tach has six wires. Thanks __________________ '72 GMC custom camper 350/350

02-26-2003, 12:28 AM	#9
Bruce68SB Registered User Join Date: Jan 2001 Location: Pomona, CA, USA Posts: 90	:p Ok- You got me. If you have drum brakes all the way around, and no warning light on your dash,. you can chuck the brake warning light switch. Drum brake trucks do not need a proportioning valve. This is because the extra braking power the front brakes need is accomplished by another method. On drum brake trucks, the front wheel [brake] cylinder pistons are larger diameter than the ones on the rear brakes. --Regards, Bruce

02-26-2003, 02:11 AM	#10
HotRod929 Registered User Join Date: Mar 2002 Location: Bondurant, IA but in Worcester, MA for school Posts: 767	Bruce68SB - I do have a warning light on my dash. I think that the thing circled in the pic is just a brake pressure warning light swich. __________________ 1970 Chevy C-20 350 V-8 Turbo 350 w/ shift kit Dana 60 w/ 4.10 gears AND Powr-Loc POSI New Additions: Summit Headers 135amp alternator Proform HEI Edelbrock 1406 600cfm carb Sunpro Tach Powr-Loc POSI Edelbrock Performer RPM Intake MSD 6A Ignition Box AIM: HotRod929 Visit My Site: http://1970chevy.netfirms.com/



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