Adjustable Brake proportioning valve - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Scrub · 05-19-2002, 12:40 AM

Today I towed a bobcat excavator home. Pretty heavy. Just for grins, I slammed the brakes on to see what was happening and I could make the front tires slide, but the rears didn't seem to do anything. Might have something to do with the rear axle bouncing on the frame making the front light and the back sucked down pretty tight to the pavement.

I have a thread up about Hydro boost master cylinders, but know I am wondering about the proportioning valve I have. It came off the donor truck that had the 2wd 1-ton front end that I have. It bolts to the crossmemer under the radiator.

I know the newer trucks have and adjustable proportioning valve that is hooked up to the rear axle and puts more brake to the rears when the rear springs are lowered by a heavy load.

Anyone know anything about these?

Thanks in advance

TW Scannell

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Scrub
70 GMC 1,000,000 + miles
72 K-20 project, 456 Dana60 front, Corp14 rear w/locker, 265R19.5 tires 20-ply. Warn 12k winches both ends, Cross-over steering with raised tie-rod, Powerbox steering, 4500 watt 120-AC power, Air, Hydraulic aux power, 4 inch lift, 5000 lb air-bags both ends.

[This message has been edited by Scrub (edited May 19, 2002).]

Duallie · 05-19-2002, 02:58 AM

I've heard that Caravans and F*#d F350's have the ride-height sensitive rear proportioning.

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Just as if I knew what I was doin'

Longhorn Man · 05-19-2002, 09:16 AM

Wow, this is interesting, I never heard of this.

------------------
'69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man
I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it.
FINALLY got the HORNIAC...a '70 one ton Longhorn with a Pontiac 350/350 and lots of 'personality'. Check out The Longhorn Webite.
E-mail longhornmail@yahoo.com
My name is Andy...not Randy...I'm in Ohio...Not Illinois...close enough?
Columbus Ohio

*Zkast* · 05-19-2002, 09:22 AM

They've been using them since 91. First started in the Grand carvans to help adjust for passenger weight.

I never thought of adding one to a full size truck though... Might just work hehe

Trouble you will run into is most of these systems were used with ABS(Anti-Lock Brake Systems)which uses 4 independant lines (one line per wheel). SO this means the rear proportioning valve assembly will have 2 lines in and 2 lines out. There's ways around that though. The mounting and hookup would be fairly simple too.

How good would it work? hmm No idea really lol. Keep in mind your dealing with drum brakes too.

------------------
Pictures and more...
piston@zkast.com
'71 LWB
350/350T, PS/PB
Special options? Yes, RUST... Need some?

Garrett - Olathe, Kansas

Scrub · 05-19-2002, 10:58 AM

I'm not sure which year I saw it, But I know my buddy's full size chevy pickup had one on the rear axle. It had to be in the early 1990's. It was a corp 14 axle with drums.

I just saw an article in Petersen's 4WD mag where Christian Hazel put a lift kit on a Toyota 4-runner and the lift caused the proportioning valve to turn the rear brakes mostly off. This is a pretty common setup.

I am more interested in an aftermarket adjustable proportioning valve, but I don't seem to ba able to find one.

Thanks again

------------------
Scrub
70 GMC 1,000,000 + miles
72 K-20 project, 456 Dana60 front, Corp14 rear w/locker, 265R19.5 tires 20-ply. Warn 12k winches both ends, Cross-over steering with raised tie-rod, Powerbox steering, 4500 watt 120-AC power, Air, Hydraulic aux power, 4 inch lift, 5000 lb air-bags both ends.

05-19-2002, 12:40 AM	#1
Scrub Collector of rusty Items Join Date: Dec 2001 Location: Sisters,Oregon USA Posts: 731	Adjustable Brake proportioning valve Today I towed a bobcat excavator home. Pretty heavy. Just for grins, I slammed the brakes on to see what was happening and I could make the front tires slide, but the rears didn't seem to do anything. Might have something to do with the rear axle bouncing on the frame making the front light and the back sucked down pretty tight to the pavement. I have a thread up about Hydro boost master cylinders, but know I am wondering about the proportioning valve I have. It came off the donor truck that had the 2wd 1-ton front end that I have. It bolts to the crossmemer under the radiator. I know the newer trucks have and adjustable proportioning valve that is hooked up to the rear axle and puts more brake to the rears when the rear springs are lowered by a heavy load. Anyone know anything about these? Thanks in advance TW Scannell ------------------ Scrub 70 GMC 1,000,000 + miles 72 K-20 project, 456 Dana60 front, Corp14 rear w/locker, 265R19.5 tires 20-ply. Warn 12k winches both ends, Cross-over steering with raised tie-rod, Powerbox steering, 4500 watt 120-AC power, Air, Hydraulic aux power, 4 inch lift, 5000 lb air-bags both ends. [This message has been edited by Scrub (edited May 19, 2002).] __________________ Scrub Sisters, Oregon - Home of the Sisters Rodeo. 70 GMC 1,000,000 + miles 72 K-20 project, 456 Dana60 front, Corp14 rear w/locker, 265R19.5 tires 20-ply. Warn 12k winches both ends, Cross-over steering with raised tie-rod, Powerbox steering, 4500 watt 120-AC power, Air, Hydraulic aux power, 4 inch lift, 5000 lb air-bags both ends.

05-19-2002, 02:58 AM	#2
Duallie Registered User Join Date: Feb 2001 Location: Nikiski, Alaska Posts: 477	I've heard that Caravans and F*#d F350's have the ride-height sensitive rear proportioning. ------------------ Just as if I knew what I was doin' __________________ Just as if I knew what I was doin'

05-19-2002, 10:58 AM	#5
Scrub Collector of rusty Items Join Date: Dec 2001 Location: Sisters,Oregon USA Posts: 731	I'm not sure which year I saw it, But I know my buddy's full size chevy pickup had one on the rear axle. It had to be in the early 1990's. It was a corp 14 axle with drums. I just saw an article in Petersen's 4WD mag where Christian Hazel put a lift kit on a Toyota 4-runner and the lift caused the proportioning valve to turn the rear brakes mostly off. This is a pretty common setup. I am more interested in an aftermarket adjustable proportioning valve, but I don't seem to ba able to find one. Thanks again ------------------ Scrub 70 GMC 1,000,000 + miles 72 K-20 project, 456 Dana60 front, Corp14 rear w/locker, 265R19.5 tires 20-ply. Warn 12k winches both ends, Cross-over steering with raised tie-rod, Powerbox steering, 4500 watt 120-AC power, Air, Hydraulic aux power, 4 inch lift, 5000 lb air-bags both ends. __________________ Scrub Sisters, Oregon - Home of the Sisters Rodeo. 70 GMC 1,000,000 + miles 72 K-20 project, 456 Dana60 front, Corp14 rear w/locker, 265R19.5 tires 20-ply. Warn 12k winches both ends, Cross-over steering with raised tie-rod, Powerbox steering, 4500 watt 120-AC power, Air, Hydraulic aux power, 4 inch lift, 5000 lb air-bags both ends.

05-19-2002, 09:16 AM	#3
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Wow, this is interesting, I never heard of this. ------------------ '69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it. FINALLY got the HORNIAC...a '70 one ton Longhorn with a Pontiac 350/350 and lots of 'personality'. Check out The Longhorn Webite. E-mail longhornmail@yahoo.com My name is Andy...not Randy...I'm in Ohio...Not Illinois...close enough? Columbus Ohio

05-19-2002, 09:22 AM	#4
Zkast Account Suspended Join Date: May 2002 Location: Olathe, Kansas Posts: 929	They've been using them since 91. First started in the Grand carvans to help adjust for passenger weight. I never thought of adding one to a full size truck though... Might just work hehe Trouble you will run into is most of these systems were used with ABS(Anti-Lock Brake Systems)which uses 4 independant lines (one line per wheel). SO this means the rear proportioning valve assembly will have 2 lines in and 2 lines out. There's ways around that though. The mounting and hookup would be fairly simple too. How good would it work? hmm No idea really lol. Keep in mind your dealing with drum brakes too. ------------------ Pictures and more... piston@zkast.com '71 LWB 350/350T, PS/PB Special options? Yes, RUST... Need some? Garrett - Olathe, Kansas



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