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  • Brake system advice needed - power drums

    I have converted my 73 to power brakes using a booster and M/C from a 77 J10 and I believe I swapped the pedal assembly (both standards) from the 77 as well. The 77 was front disc, but my 73 was manual drum/drum. I kept and will be keeping the drum brakes. I didn't upgrade any wheel cylinders, and the original junction block is still there. I bought residual valves long ago but never put them in. That was all over 15 years ago.

    Well, the reman M/C I had bought has been leaking for some time and I finally got around to fixing it. I thought it might be a good time to evaluate the whole system and maybe do it right in case it's not as it should be now.

    So my questions are: should I have upgraded the wheel cylinders since I went to power brakes - not simply change them but should they be different than the ones for manual setup?

    I assume the disc/drum M/C is fine for a drum/drum setup, but if not, let me know.

    Is leaving the original junction block there fine?

    Everything works fine, the pedal has always felt a little stiff for a power setup but not bad. It stops decent and I can lock them up if I need to. Basically all I changed was the M/C, the pedal, and added a booster. Nothing else was done/changed. I've never been sure if it was done "right" though, so any thoughts are welcome.

    Thanks!
    1973 Wagoneer 4.6 I-6 stroker, t176/d300, offy dualport w/ quadrajet, pertronix, flowmaster

    "Roads? Where we're going we don't need roads." -- Doc Brown https://forums.ifsja.org/core/images/smilies/cool.png

    "When this baby reaches 88 miles per hour, you're gonna to see some serious shhttps://forums.ifsja.org/core/images/smilies/eek.pngt!"

  • #2
    I did the same thirteen years ago with my also 73' j4000
    Only used a MC and booster from a old Bedford I just had laying around.
    Did put a adjustable proportion valve in the brake line to the rear wheels so I could adjust the braking force when the truck bed was loaded or unload or else the rear wheels kept locking up all the time!

    Later on when the Bedford booster and mc got worn-out I switched to a booster with MC from a modern Volvo V70
    Had to remake the bracket to the firewall and the rod from the booster to the pedal , but everything did work fine.
    Jeep "because mother nature hates flat roads to"

    http://www.ifsja.org/forums/vb/showthread.php?t=180974

    99' Dodge ram 2500 4x4 crew cab 5.9 Cummins ,backup work truck for now
    73' Jeep J4000 (named Heep or Desert Dragon) amc 360 V8 converted to LPG with T15/D20 (was my daily work truck for thirteen years and is getting major overhaul at the moment!)
    80' Jeep cj5 350 V8 Chevy/sm420/D300 project
    70/71 Jeep J4000 parts truck with Buick 350

    Former vehicles:
    85' Volkswagen caddy mk1 1.6 diesel.
    83 Toyota land cruiser BJ42 3.4 diesel.

    Comment


    • #3
      Drum brake master cylinders typically have a residual valve for each circuit that keeps the shoes closer to the drum when the brake is released. This makes for faster response, ie less pedal before braking. If you look at the '74 TSM, the check valves are shown in the drawing of the CJ master cylinder. The check valve will be missing from the disk brake circuit.

      The '77 would have also had a combination valve that is described in the TSM at the Tom Collins site. It included a metering valve, proportioning valve and pressure switch for the warning light. I presume you are not using this part. You can read about this in '77 TSM.
      Tim Reese
      Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
      Browless and proud: '82 J20 360/T18/NP208/3.73, Destination ATs, 7600 GVWR
      Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
      GTI without the badges: '95 VW Golf Sport 2000cc 2D
      ECO Green: '15 FCA Jeep Cherokee KL Trailhawk

      Comment


      • #4
        Tim, do you think I need that part?
        1973 Wagoneer 4.6 I-6 stroker, t176/d300, offy dualport w/ quadrajet, pertronix, flowmaster

        "Roads? Where we're going we don't need roads." -- Doc Brown https://forums.ifsja.org/core/images/smilies/cool.png

        "When this baby reaches 88 miles per hour, you're gonna to see some serious shhttps://forums.ifsja.org/core/images/smilies/eek.pngt!"

        Comment


        • #5
          That part, as in the residual check valves or the combination valve?

          Looking at the parts book, it seems that FSJs were only offered with disks and power brakes after 1973. That is, you could get 4-wheel drums '74-76 but only with manual brakes. You could get a CJ with drums (LDB) and power brakes (WPB) through '77. I expect this is the setup you want to follow. It looks like the check valves in the CJ LDB/WPB were deleted by '77, and replaced with a chassis-mount combination valve. This LDB valve has two sections, a warning switch and a rear proportioning valve.

          Probably I'd start with the disk-drum master and the drum-drum combo valve, and see how it works. Suggest you also read this section in the '76 TSM and think about what's going on here. Apparently Jeep eliminated the check valves behind the tube seats, shown in the '74 TSM.

          Weight distribution of a wagon is not terrible, so you might not need the proportioning valve. You could use the existing plumbing and see how it goes.
          Last edited by tgreese; 06-05-2022, 11:58 AM.
          Tim Reese
          Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
          Browless and proud: '82 J20 360/T18/NP208/3.73, Destination ATs, 7600 GVWR
          Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
          GTI without the badges: '95 VW Golf Sport 2000cc 2D
          ECO Green: '15 FCA Jeep Cherokee KL Trailhawk

          Comment


          • #6
            Originally posted by tgreese
            It looks like the check valves in the CJ LDB/WPB were deleted by '77, and replaced with a chassis-mount combination valve. This LDB valve has two sections, a warning switch and a rear proportioning valve.
            My 73' j4000 did have that when I got it and it looked like it was there for a long time.
            Also front and rear drum brakes and no brake booster behind the mc.
            (Also no power steering)

            I did put a mc with the same diameter on as the jeep mc and also a booster. (The jeep mc was leaking inside and not repairable)
            Put the adjusteable proportioning valve on the rear brake line and in front of the proportioning valve.
            It was braking perfect , but you had to know how to push the pedal or else locking up the rear wheels.
            Jeep "because mother nature hates flat roads to"

            http://www.ifsja.org/forums/vb/showthread.php?t=180974

            99' Dodge ram 2500 4x4 crew cab 5.9 Cummins ,backup work truck for now
            73' Jeep J4000 (named Heep or Desert Dragon) amc 360 V8 converted to LPG with T15/D20 (was my daily work truck for thirteen years and is getting major overhaul at the moment!)
            80' Jeep cj5 350 V8 Chevy/sm420/D300 project
            70/71 Jeep J4000 parts truck with Buick 350

            Former vehicles:
            85' Volkswagen caddy mk1 1.6 diesel.
            83 Toyota land cruiser BJ42 3.4 diesel.

            Comment


            • #7
              Thanks guys! I spent some time yesterday on oljeep looking at the tsm's but just for the sj'$. I'll check out the 76 cj area a little closer. Appreciate the help
              1973 Wagoneer 4.6 I-6 stroker, t176/d300, offy dualport w/ quadrajet, pertronix, flowmaster

              "Roads? Where we're going we don't need roads." -- Doc Brown https://forums.ifsja.org/core/images/smilies/cool.png

              "When this baby reaches 88 miles per hour, you're gonna to see some serious shhttps://forums.ifsja.org/core/images/smilies/eek.pngt!"

              Comment

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