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3/4 ton brakes on 1/2 ton

Discussion in 'The Garage' started by jeff l, Jul 21, 2006.

  1. jeff l

    jeff l 1/2 ton status

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    I have a 86 FS Jimmy that I put 3/4 ton axles on, when i go to stop the brakes shake the truck a little. do i need to change the p -valve or the master cylinder to 3/4 ton.

    I had one roter turned and the other got changed with the hub.
     
  2. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Sounds like runout in the rotors. Have the rotors machined and it will go away.
     
  3. jeff l

    jeff l 1/2 ton status

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    the roter i had turned probably should have been replaced. I am going to check it tonight w/ dial indicator.

    besides that do you know if the 1/2 ton p- valve should work on the new 3/4
     
  4. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Did you machine the new rotor? I do this for a living and you wouldn't believe how many new rotors i found crooked. I did the 3/4 ton swap then on to 1 ton and still using the same prop valve and master with no problems.
     
  5. jeff l

    jeff l 1/2 ton status

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    thanks I will check both--- I wouldn't have thought of that. good to hear about p valve and master ; I have so many new parts on the rebuild and different years its hard to tell whats wrong when nothings the same.
     
  6. sweetk30

    sweetk30 professional hooker Premium Member

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    good test is when hitting brakes if the seat or floor vibes its most likly the rears 90% of the time. then if the steering wheel vibes back and forth its the fronts.

    those rotors are cheep and if you take it that far apart just pop on some new ones.
     
  7. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    New rotors need to be machined as well, 1st reason is that they need to be mounted on the hubs then machined to be true and 2nd reason is new rotors get shipped and dropped and are usually crooked.
     
  8. sweetk30

    sweetk30 professional hooker Premium Member

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    i work auto mechanic as well and have so for over 8 years. i have only had that problem at most a dozen times in my life. most come with the nondirectional finish on them to help break in and seat pads good.

    plus why buy a new rotor and cut them as it is not as thick now and will warp out quicker than the new one.

    and dont buy the cheep junk rotors . get atleast mid grades thay will be better and last longer with less problems.

    p.s. autozone SUCKS !!!!!!!!!
     

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