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difference between 1/2 and 3/4 brake master cylinder?

Discussion in 'The Garage' started by sandracer0004, Jan 28, 2004.

  1. sandracer0004

    sandracer0004 1/2 ton status

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    whats the difference? should i upgrade the master, and the booster on my half ton,

    i have replaced everything else so far

    3/4 disk calipers, proportion valve, rear disks as well.
     
  2. bablazer73

    bablazer73 1/2 ton status

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    The booster is the same., the size of the piston is larger on a 3/4, because the wheel cylinders are larger. You should use the 3/4 master cyl.
     
  3. Triaged

    Triaged 1/2 ton status

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    77 K10 w/ 350

    Item#: TSM101521
    Price: $ 17.99
    Attributes: Brake Master Cylinder - Remfd
    # of Line Ports: 2
    Bore Size: 1.12500''
    Line Thread Size: 9/16-18, 1/2-20


    77 K20 w/ 350

    Item#: TSM101534
    Price: $ 21.49
    Attributes: Brake Master Cylinder - Remfd
    # of Line Ports: 2
    Bore Size: 1.12500''
    Line Thread Size: 1/2-20, 9/16-18
    Comments:GM Code JB7 (Power Brakes, 8,400 LB., Tandem Diaphram Booster)

    That is from NAPA.
    Looks like the master's have the same bore but the 3/4-ton has the front/back fittings swapped. It also looks like the 3/4-ton uses a dubble diaphram booster which will make for less peddle effort.
     
  4. BobK

    BobK 1/2 ton status

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    Triaged....the M/C bore king! /forums/images/graemlins/grin.gif
     
  5. sandracer0004

    sandracer0004 1/2 ton status

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    pretty cheap, i mine as well just replace the master for that price. ive already replaced everything else.
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    If the fittings are swapped, I'm guessing it's an entirely different MC, like a plastic reservoir/aluminum body vs. the cast style. Were they even using the plastic/aluminum MC's back then?

    My '85-88 parts manual lists 3 different MC designs for the C/K/R/V trucks, aluminum, and two cast iron versions.
     
  7. jwduke

    jwduke 1/2 ton status

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    No, they were still the steel ones. I don't think they were aluminum/plastic till the new body style came in '81
     
  8. Triaged

    Triaged 1/2 ton status

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    /forums/images/graemlins/tongue.gif

    Sorry for wanting to save someone $20...





















    ...just to make them spend $100 on a 3/4-ton booster /forums/images/graemlins/crazy.gif /forums/images/graemlins/waytogo.gif
     

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