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Dual Range Hydra-Matic rebuild

Discussion in 'The Hokey Ass Message Board' started by jet 02, Oct 5, 2019.

  1. jet 02
    Joined: Mar 1, 2013
    Posts: 2

    jet 02

    Does front drum need replacing??

    I am starting to gather parts for a '54 cad trans rebuild. (smells burnt) Will be going into a '50 Cad behind a '58 Cad 365. The victim transmission was built for the strip. Came without belhousing so do not know it's last application.
    I need to go back stock. I have '55 chevy truck and '54 Lincoln Hydra matics for donors.
    I think I now have the correct front, rear, inner and outer valve body assemblies. for a '54 cad.
    The next Question, is that with valve bodies removed from the Cad and Lincoln, it looks like there are fine groves in the front drums. where the band rides. They both look like they were turned on a lathe. All the drums I have seen, that have been removed are smooth as a baby's' bottom. So are the groves a result rebuilder machine work, or from the front band slipping? Do they need replacing? (front band screws are cranked down more than normal)
    Sad but from what I have seen, all drums that have been removed and "stored inside" are rusty..
    Parts Have 9 new stock paper and cork wavy frictions and a few rabestos and a pair of Dynaflow "grip right now" frictions. Pair of good bands from a "55 olds,.

    I have the Paul Marsh manual, Paul Rank manual, and factory manuals.

    The Drum condition is my question, Again, They both look like they were turned on a lathe.

    Any comments appreciated

    warbird1 likes this.
  2. jet 02
    Joined: Mar 1, 2013
    Posts: 2

    jet 02

    Answer myself.. Well I opened up the '55 GMC.. The front clutch has thin dark lines around it where the front band rides,
    but is smooth to the touch.
    So the "grooves" mentioned above are probably low areas due to the original machining.
  3. Homemade44
    Joined: Feb 7, 2007
    Posts: 526


    If I remember correctly B & M used the duel range hydro for the starting point of their racing transmission.
    I have a 1958 Bentley that uses a modified duel range hydro from GM. It used wave friction plate to make the shifting smoother than the original GM transmissions. I can't answer your question on the grooves as I have never been inside of one. The transmission in my Bentley shifts hard like the early Olds did so I think it has flat plates installed during a rebuild. I will be watching this thread to learn more about the transmissions. I have a Bentley manual that has a lot of information on the transmission.

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