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Remove or repair height sensing rear brake proportioning valve?

Discussion in 'The Garage' started by DieselSub, Jan 27, 2005.

  1. DieselSub

    DieselSub Registered Member

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    My 85 K20 came equipped with a height-sensing rear brake proportioning valve. The valve is connected via an arm to the rear axle, and varies rear brake pressure according to load.

    After 20 years of service, it's decided to start leaking. I'm also getting a warning buzzer when I press the brakes and the engine's running.

    Should I replace this? Or bypass it and run the standard 3/4 ton setup where the front proportioning valve does all the work? What have other people done when lifting a truck with this setup?

    Also, does anyone know the right part number. My local GMC dealer "thought" the GM part number was 1257203, but he wasn't sure. Anyone know for sure?

    Thanks
     
  2. AkMudr

    AkMudr 1/2 ton status

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    I had the same thing for a while but cut it down and ran a SS line from the frame to the ""T" block. Brakes work MUCH better now
     
  3. sweetk30

    sweetk30 professional hooker Premium Member

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    carfully remove this item and take a special big hammer and beat it to death!!!!!!

    ditch that thing!!!!!
     
  4. AkMudr

    AkMudr 1/2 ton status

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    If yer lookin for the brakelines to bypass that valve let me know, I got mine from www.amstreetrod.com and I have all the part #'s needed to get rid of it.
    I used a 40" Earls line (Whcih will actually be too short when I put on anotehr 4" so I will hafta tap another line into it and extend it) with an Earls adapter then a 7/16's adapter from the line into the "T" Cost me about 50$ but I also replaced the "T" block
     
  5. DieselSub

    DieselSub Registered Member

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    Has anyone had any problems with the rear tires locking up when they remove the valve? The only write-ups I've seen (of Toyotas) shows people replacing the valve with a manual proportioning one so they can tune the rear lock up.

    But, from what I'm hearing I'll probably just dump the valve and plumb the two lines together...

    Thanks for all the input!
     
  6. AkMudr

    AkMudr 1/2 ton status

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    Mine are alot more sensitive but you just learn to adjust yer braking style
     

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