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Thread: Power Brake Lock up!!

  1. #1


    Added power brakes last fall. New lines, wheel cylinders, a J-4000 booster setup. Works great with one exception. If ya ain't careful, you will lock all the tires up with only very little pedal push. Did I miss someting in this setup? Maybe some kind of proportional valve or something? Things work great, but eatin' the windshield is getting old. I mean I can literally lock all four tires at 60 mph and come to an instant halt. But when you are trying to stop say at the end of he street, wham! you stop instantly. Any ideas out there?


  2. #2
    Join Date
    Dec 2003
    parsons Kansas


    sounds like your mastercyl was designed for larger wheel cyl. and maybe discs. pushing way more fluid than needed to do the job on the 715s. may step down to a j-3000 mastercyl. or your part store guru may be able to match wheel cyl. sizes with master cyl. piston sizes and come up with somethin that will work for you. hope this helps some.
    67 M725, 67 M715, 68 M715

  3. #3


    Leave it together and back down the adjustment a little. What pads did you use? Maybe run the booster to a less signal vacuum port. What tires do you have? If your running stock NDT's the don't have a lot of tread contact with the road to begin with.
    Big Blocks RULE!

  4. #4


    I believe the J trucks share the same system as the wags. There is a brake proporting valve on the frame under the drivers side firewall. You might try one of those. I think BJ's offroad has them new. It might help.

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