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Old 03-14-2011, 07:40 PM   #1
383_Gladiator
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can anyone tell me what this does?

Its on an 84 GMC 4x4 frame i just bought. i know it has something to do with brakes but Ive no idea what its for. I have worked on older 73-79 chevy 4x4's and never seen this. do i need it?

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Old 03-14-2011, 08:07 PM   #2
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Re: can anyone tell me what this does?

Yes, it's a load activated brake system. You can find those under heavy halfs and heavier trucks. I don't know the full details. It does adjust brake pressure to the rear when the truck is weighted down. Do you plan to carry heavy loads?
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Old 03-14-2011, 08:11 PM   #3
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Re: can anyone tell me what this does?

probably be towing my 20 foot searay and camping gear. but Ive swapped in 1 ton axles and hydroboost.
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Old 03-14-2011, 08:14 PM   #4
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Re: can anyone tell me what this does?

Thats right, the more weight on the rear end (the more the rear suspension compresses) the more pressure is available to the rear brakes. You can remove it but you may need to replace the propotioning valve with one from a truck that did not have this valve, or install an adjustable prop valve in its place to get the correct pressure to the rear brakes.
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Old 03-14-2011, 08:16 PM   #5
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Re: can anyone tell me what this does?

i had planned on a new proportioning valve as i have front and rear discs. no more big drums on the 14 bolt.
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Old 03-14-2011, 08:28 PM   #6
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Re: can anyone tell me what this does?

My dually *had* that factory. I think my 84 had it too. Took it off never looked back.
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Old 03-14-2011, 08:44 PM   #7
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Re: can anyone tell me what this does?

whats the best way to remove it? as far as bridging the gap between the 2 lines?
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Old 03-14-2011, 08:57 PM   #8
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Re: can anyone tell me what this does?

just splice them together with a union fitting
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Old 03-14-2011, 09:03 PM   #9
383_Gladiator
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Re: can anyone tell me what this does?

do they make them for 2 different sizes? one fitting is larger than the other.
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Old 03-14-2011, 09:11 PM   #10
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Re: can anyone tell me what this does?

if the actual lines are buth the same size (should be 3/16) then you can use this. if not, cut the line before the valve and run that line right into the splitter block on the alxe
http://images110.fotki.com/v559/phot...onunion-vi.jpg
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