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Technical Pitman master spline geometry question

Discussion in 'The Hokey Ass Message Board' started by 69fury, May 21, 2020.

  1. 69fury
    Joined: Feb 24, 2009
    Posts: 1,419

    69fury
    Member

    Hey guys, I had a stock 62 falcon, the steering column shaft pointed down into the box, 90degrees later, the pitman pointed forward and down, swinging left to right, to steer the front tires from behind the hub centerline.

    Later, I got a 61 falcon with a 65 chevy van i beam axle on leaves. It had some ghastly draglink style steering that someone pulled and mounted a stock falcon box back on the frame, but they didnt know how to connect it to the chevy van axle with a big V8 in the way. I've got that all worked out except one thing......

    When the box is centered, the pitman master splines key the arm so that it's not pointing directly ahead when the tires are. I believe it's due to the pitman arm pointed down towards the contact patch of the tires in stock application, but cant work out why. All the streed rod steering diagrams show 90degree angle setups but they arent detailed enough to know if that's a generalization.

    Does anyone know why OEM master splines would not point the pitman straight ahead? It would seem to provide more steering angle in one direction or another.

    Thanks,
    rick
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 50,174

    squirrel
    Member

    Are you sure the parts are all OEM for that car?

    I've seen the splines twist on a pitman shaft, but not that far...
     
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  3. seb fontana
    Joined: Sep 1, 2005
    Posts: 7,198

    seb fontana
    Member
    from ct

    I am pretty sure that the Pittman arm should point strait forward if the steering shaft is centered; pretty much all Fords, falcons, must, comet, fairlane, Maverick, in about a 30 yr spread.. I can tell you that a pittman arm from a '57 Ford is the exact same as one for a '72 Comet! :).. If there are the wide splines in four places to index the arm just grind them out and position arm where you want it.
     
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  4. 69fury
    Joined: Feb 24, 2009
    Posts: 1,419

    69fury
    Member

    That's definitely the plan, unless someone came here with a great reason for the four master splines to be off. Thanks!
     

  5. 69fury
    Joined: Feb 24, 2009
    Posts: 1,419

    69fury
    Member

    I hadn't thought about a twisted spline shaft before because the exposed portion appears to be mint. Have you ever seen or heard of one twisted inside the box with not even a trace of exposed shaft twist? Should I be nervous about this box? Would be a shame, the falcon box is so compact.
     
  6. It would take a lot of torque loading to twist a pitman shaft.Not sure you could generate it.Look at what it takes for a race car to twist a axle shaft.I think the input shaft would twist first since its a thinner shaft.
     
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  7. squirrel
    Joined: Sep 23, 2004
    Posts: 50,174

    squirrel
    Member

    Is the missing spline straight ahead when centered?

    Sent from my Trimline
     
    69fury likes this.
  8. 69fury
    Joined: Feb 24, 2009
    Posts: 1,419

    69fury
    Member

    That detail I dont recall, I'll have to check when I get back out to the barn. Just now getting back to work on this. I only remembered that the smaller pitman arm eye wasn't straight ahead of the large one when the box was centered. Maybe someone had it apart and didnt align it perfectly?
     
  9. TRENDZ
    Joined: Oct 16, 2018
    Posts: 310

    TRENDZ

    How can you be sure its a stock steering box or pitman arm? It may be a van box/arm, or who knows what else? Maybe in a different application, the box mounted at a different angle. The outer appearance is just the first indicator of what you might have there.
    It’s a good thing you seem to have a handle on what you need to do. Some would just slam it on there. Hope you get the mystery solved.
     
    69fury likes this.

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