77 Diplomat Control arm mount

M Body General Discussion

  1. TechNoGeek

    TechNoGeek Member

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    On a 77 Diplomat, The Control arm is what mounts the upper A Arm right??
    The way the Control arm mounts is my question, What does it Bolt to?
    I cannot see unless I take it all apart.
    Does anyone have a Parts picture and maybe some part numbers?
    Is that plate it bolts to replaceable?
    Technogeek
     
  2. Aspen500

    Aspen500 Well-Known Member

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    There is a bracket (plate) that bolts to the k-frame with 4 bolts. The upper control arm attaches to it with the two vertical nuts. The bolts have plates on them so they won't turn when loosening the nuts. The top of the shock is also attached to the plate or bracket. Yes, it is replaceable.

    Here's a pic of my Aspen (Diplomat is exactly the same). You can see the bracket and one of the bolts that hold it to the k-frame. Disregard the arrow. It was for something else. I know I've got a better pic but can't find it right now so................. DSCF0013.JPG
     
  3. Aspen500

    Aspen500 Well-Known Member

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    Hold on, here you go. Parts illustration and p/n's
    DSC00276.JPG DSC00277.JPG
     
  4. volare 77

    volare 77 Well-Known Member

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    I probably have a good used support plate if you can`t find one locally.
     
  5. Raff

    Raff Well-Known Member

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    Here is a pic of the arm, the pivot bar and mounting bracket. The round hole in the bracket is where the upper mount of the shock attaches.
    img_0633-jpg.jpg
     
  6. TechNoGeek

    TechNoGeek Member

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    Mine does not have Bolts that are Vertical that go into the frame as shown, my mount bolts are horizontal.
    Technogeek.
     
  7. TechNoGeek

    TechNoGeek Member

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    I will take it apart to verify tomorrow. I don't want to waste any ones time speculating.
    Technogeek
     
  8. TechNoGeek

    TechNoGeek Member

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    I found my issue. The support plate is damaged. I will try to weld it.
    Thank you guys your Great helping me like this!
    One followup question.
    The Upper Ball joint seems to have threads that looks like I can unscrew it.
    Can I unscrew it? Should I? Should I leave it alone?
    Just wondering.... It would help reassembling everything if I can disconnect the Upper Ball joint from the A-Arm.
    Technogeek.
     
  9. Raff

    Raff Well-Known Member

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    I would separate the ball joint stud from the steering knuckle, the upper shock bolt and the four bolts holding the mounting plate. Then you can remove the entire assembly and work on a bench. No need to remove the ball joint unless you’re replacing it. You’ll need the appropriate socket and a big breaker bar

    F30106E9-19FC-4059-A0E1-7D605A7FF6DF.jpeg
     
    Last edited: Jun 5, 2019
  10. volare 77

    volare 77 Well-Known Member

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    IIRC, those support plates were a part of a recall in 76 or 77. I think they added brackets c3940106 for extra support to help with the cracking.
     
  11. BudW

    BudW Moderator Staff Member

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    I would avoid welding the damaged plate. Not that I doubt anyone welding skills, but as important as the plate is, I would recommend if you can find a used one, first. I would think a few members here would have one for sale.
    If a person wants to gusset or reinforce a used plate, then I would be all for that.

    Also, if you can find the parts for the F-body recall, then that would be a plus (not a requirement, but a plus).


    The ball joint really has nothing to do with or is in the way of removing (or replacing) the plate.

    When the weight of the car is not on the ball joint, check it for looseness. If ANY play present to upper ball joint – then change that joint.

    Chrysler used a couple of different size ball joint socket sizes. If you find one that mentions B or E-body, then you are good. The C-body and pickups use a larger size and the older A-body (I think) use a smaller size.
    The socket is a square with rounded corners:
    Ball Joint Socket.jpg
    I have the measurements at home. A person can use a large Crescent wrench and/or large end wrenches, if you have one, but the ball joint socket works the best. The O’riellys auto parts store near me rents them out (no promise the parts store close to you has it).
    The only thing this socket fits is Mopar ball joints, so it is silly to purchase one and use it once.

    You will need a long breaker bar that is two-foot long (minimum) and three-foot long preferred. You will also need to loosen/remove ball joints with arms still attached to the car – for removing the joints off the car is, um, difficult. On the bench and with arm in a vice, you will find the work bench will start moving a long time before the ball joint starts to break loose (moves).

    The specs say to tighten the ball joint until it bottoms out on arm, then tighten to 125 Ft/lbs. That said, it takes a lot more than 125 ft/lbs torque to loosen or remove most upper ball joints.
    BudW
     
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