Who has Dr. Diff 8 3/4 rear discs? Pt. 2

Brakes for your Classic Mopar

  1. jbc426

    jbc426 Well-Known Member

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    On one car, I had to put the washer's between the rear end housing adapter and the caliper bracket.

    The caliper does "float" to some degree to equalize the clamping force, since the piston is only on one side of the caliper.
     
  2. my68barracuda

    my68barracuda Well-Known Member

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    I looked closely at the distance between the pads and the the rotor side and used the washers to center the pads to the rotor. It did not take much to do that and probably not causing the brake issue that your are dealing with.
     
  3. my68barracuda

    my68barracuda Well-Known Member

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    agree, with parts today, anything is possible, but these distribution blocks on the drum - drum cars are exactly that, a simple two chamber distribution block with a piston sensor between the two chambers that activates to turn on the 'Brake' light if there is a pressure difference between the two chambers.
     
  4. Car Nut

    Car Nut Mopar Master

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    True, I bought two new ones and both O rings were messed up.
     
  5. Needswork

    Needswork Well-Known Member

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    Although not the cause of the poor brake performance, your parking brake cable connection under the dash is installed incorrectly as pointed out by Cal from Australia. Once you get the "real" problem figured out, you'll want to fix that.
     
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    • Kern Dog

      Kern Dog I like girls that wiggle FABO Gold Member

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      6 2020 E.JPG
       
    • plumkrazee70

      plumkrazee70 Well-Known Member

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      Thank you. I see what I did, I went over the axle tube. I'll get that fixed this week and and fix the parking brake handle.

      Thanks, for everyone's help. This has been driving me insane.
       
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      • Jeffrey67dart

        Jeffrey67dart Well-Known Member

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        The e-brake cable routing is indeed wrong. Maybe it is / was under tension that way. Sometimes if you pull the lever on the e-brake first, and then push the regular brake pedal. It is messed up. Then you must try to push the piston back, and pump the piston/brakepad to the disc with the pedal. After that you can try the e-brake.
         
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        • plumkrazee70

          plumkrazee70 Well-Known Member

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          Ok, There is zero change after fixing the following:

          I got the parking brake cables re routed
          I fixed the brake handle
          I lubricated the caliper slides

          What I know:
          With the parking brake engaged, I can not move the wheel by hand.
          With the parking brake disengaged, I can move the wheel by hand.
          With the car idling in Drive, the wheel will not stop with the parking brake applied, or the brake pedal applied or both.
          There is a mechanical and hydraulic problem.
          I know the cables are engaging the caliper (see videos)
          I know the pads are NOT contacting the rotor surface, entirely. (See pictures of pads) This has to be the problem, but I have no idea how to fix. The only thing I did not do was put another washer to move caliper bracket closer to rotor, only because I didn't have any on hand.

          Thanks again for any advice.

          Drivers Side E brake

          Passenger side E brake

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        • my68barracuda

          my68barracuda Well-Known Member

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          here is a post on adjusting the Mustang Cobra caliper pistons. You should be able to find others with more detail, but it appears that setting the parking brake adjusts the caliper piston, so now that you have the parking brake cables routed properly set and release the parking brake a few times an see if that helps.

          I would also check again to be absolutely sure the rear brake lines are bled and have no trapped air.

          Adjusting rear brakes - 94 Mustang disc calipers.
           
        • plumkrazee70

          plumkrazee70 Well-Known Member

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          Trust me, I've pulled the parking brake handle so many times thinking the same thing. I guess it's possible th pad pin is not sitting in the piston the right way. I'll look at that tonight. I'll also make sure they are completely bled, again.

          What do you make of the in even pad wear?
           
        • my68barracuda

          my68barracuda Well-Known Member

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          the pad wear looks OK its going to be light, remember this set up is a Ford Caliper on a Toyota disk,, they fit together and work together, but each was not designed with the other in mind..
          If you are still having problems after re bleeding the brakes I would be back with Dr Diff.
           
        • plumkrazee70

          plumkrazee70 Well-Known Member

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          I was more looking at the light wear at the bottom and not anywhere else.
           
        • plumkrazee70

          plumkrazee70 Well-Known Member

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          So I checked the pad pin in relation to the caliper piston and everything looks correct. I also placed a small piece of wood in between the piston and the caliper (with the caliper off) and pumped the pedal a few times and the piston moved just fine, so I know its working like it should.

          I know the factory drum brake distribution valve is just a switch, but how do I test that to make sure its not closed? Take my meter and put it on the screw where the wire goes and then to ground?
           
        • my68barracuda

          my68barracuda Well-Known Member

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          If you are getting fluid through it when you bleed the brakes, it is ‘working’
           
        • my5thmopar

          my5thmopar Life Long MOPAR Owner FABO Gold Member

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          @plumkrazee70

          Did you fix this? What's the solution? I thought about buying these but...waiting if there's an issue with the setup.
           
        • plumkrazee70

          plumkrazee70 Well-Known Member

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          It's better, but not as it should be in my opinion. I rebled with a pressure bleeder and that made a big difference. I do believe, I have some stubborn air trapped somewhere. I am almost done getting a few little things buttoned up so I can take it for a short drive and re bleed.

          I wouldn't hesitate on the kit at all, it's really nice and reasonably priced.
           
        • 72bluNblu

          72bluNblu FABO Gold Member FABO Gold Member

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          I run DoctorDiff's 11.7" rear disks on my Duster. They work great. My full system is a set of DoctorDiff 13" cobra style brakes up front, the 11.7's in the back, a 15/16" master cylinder (also DoctorDiff), and an adjustable proportioning valve from Summit (looks like a wilwood piece, but summit brand).

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        • my5thmopar

          my5thmopar Life Long MOPAR Owner FABO Gold Member

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          What about the necessity of a parking brake? I don’t have a working one now but, it’s on my list of things to do.
           
        • plumkrazee70

          plumkrazee70 Well-Known Member

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          Everything I read, says that it is necessary with those type of calipers. The good thing is that Dr. Diff's parking brake cables ($100) mount right up to the factory equalizer.
           
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          • goldduster318

            goldduster318 Overzealous Car Modifier

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            They will take a while to break in and have everything be flat to the rotor surface. The way the calipers move when applied means that it will not wear evenly from day one. I doubt everything is perfectly flat. I needed to drive mine a little before that happened also. They will work better after they break in.

            If you have an adjustable proportioning valve, also make it wide open for now.
             
          • Blucuda413

            Blucuda413 Well-Known Member

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            I hate to mention this but i will. Do you have the bleed valve pointed up when bleeding the caliper? It will not bleed correctly without it pointed up even if you have to take the caliper off the rotor. Seems like I had that problem years ago!!
             
          • plumkrazee70

            plumkrazee70 Well-Known Member

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            Mine are definitely pointed up. Thanks tho
             
          • plumkrazee70

            plumkrazee70 Well-Known Member

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            UPDATE: I had the car aligned and the brakes looked at. Turns out the banjo copper washer was seeping, so I wasn't getting full pressure to the caliper. Fixed that, rebled and the pedal is high and hard and stopping great.

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            • my68barracuda

              my68barracuda Well-Known Member

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              Nelson’s looks to be an old school car shop, those are nice to have around.
              Just one question, is the Nelson proprietor a Ricky or Admiral?
               
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