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new rear drum brakes getting hot on a one ton truck after rear end swap

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  • new rear drum brakes getting hot on a one ton truck after rear end swap

    Background info: I just swapped a dana 80 dually rear end out of a 1997 ram 3500 into my 93 Dodge D350 to replace the old Dana 70. THe old rear end had 12" drums, the new has 13" drums.
    I put in new drums, shoes, wheel cylinders, adjusters, all springs and hardware, and E brake cables. Bled the brakes and the pedal feels good.

    Took it for a 120 mile drive last night, and after a while the brakes would vibrate/pulsate upon application of the pedal. I tried stopping with the parking brake to verify if it was the rear brakes doing the shaking, and it was.
    When I got home, I pulled into the shop, and the drums were so hot I could smell them. I pulled the wheels and rotated the drums and felt or heard zero shoe to drum contact. I verified that the Ebake was fully releasing, and backed off the E brake cable adjustment, and backed off the brake adjusters about 1 turn each.
    Drove it 15 miles to work this morning, and when I slowed down to get off the highway and turn into the parking lot, it shook. I felt the drums, and the left one was hot, the right one was cold.
    Maybe I need to back off the adjuster a little more, but it seems strange that it is getting hot when there was no apparent shoe/drum contact in the shop, plus the adjuster backed off some from that point. The cool drum on the right side gives me hope.
    Does anyone have any ideas of why this is happening, or had anything like that happen before? Could air in the brake line do that? If the wheel cylinder is a different size, could that have an effect? Is the fluid not returning to the master quick enough for some reason, causing the brakes to drag, but then be fully released by the time I get it jacked up?
    Any ideas would be appreciated.
    Thanks, Joel

  • #2
    when working on old cars, there are usually two things that cause dragging brakes. A restricted brake line, such as a rubber hose that the inside is swelled shut. Or the brake pedal or booster adjustment, if it has no free play it covers the return port in the MC, so as the fluid expands from heat, it is trapped and operates the brakes.

    My fabulous web page

    "If it don't go, chrome it!" --Stroker McGurk

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    • #3
      I hope it's not a bearing problem...
      ...

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      • #4
        Thanks Loren, I inspected and packed the bearings well, and the hubs were not as hot as the drums, so I think they are OK. Squirrel, it did not do this before the swap, it there something about a swap that could exacerbate the pushrod length thing? Like different sized wheel cylinder bores, or bleeding the brakes messing up the proportioning valve?
        Last edited by Hemi Joel; January 20, 2015, 11:42 AM.

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        • #5
          I don't know of anything....but I wasn't there, either. Is it possible you crimped a hard line somewhere?

          My fabulous web page

          "If it don't go, chrome it!" --Stroker McGurk

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          • #6
            maybe the other brake isnt working?

            a 10-15 mph lock up on a dirt road can tell ya what brakes are working sometimes.

            extremely hot and parts turning blue after a ride,..yup they're dragging.

            might try bleeding the T fitting also?

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            • #7
              I pried the drums off a '68 Ranger to find the adjusters were in backwards...
              Flying south, with a flock of bird dogs.

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              • #8
                Solved! I went to re-bleed the brakes, and instead of draining into and old dirty jar of brake fluid, I used a clean jar and fluid. Right away I noticed that the fluid coming out of the bleeder looked milky. It must have had a lot of moisture in it. So I sucked the fluid out of the master with a syringe, and flushed it all out of the lines. Bled them out and it works fine! Thanks for all the replies.

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                • #9
                  And we have now proved for certain that water is compressible and will expand when hot. Very good!

                  Of all the paths you take in life - make sure a few of them are dirt.

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                  • #10
                    Originally posted by Beagle View Post
                    I pried the drums off a '68 Ranger to find the adjusters were in backwards...
                    I've had that before, but it loosened the brakes over time.

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