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Technical Pittman arm question

Discussion in 'The Hokey Ass Message Board' started by BamaMav, Aug 4, 2021.

  1. BamaMav
    Joined: Jun 19, 2011
    Posts: 5,112

    BamaMav
    Member
    from Berry, AL

    So, I finally got to drive my car today with the swapped in Saginaw power steering box. The box came from a 85 Firebird, the Pittman arm is off a S 10 pickup, column is GM with a stock 67 Chevelle wheel. The steering is quicker than the worn out manual 1947 Lincoln box was and smooth as silk, but I have lost a good bit of turning radius, it doesn't turn as sharp as the old manual box did. I'm thinking maybe I need a longer Pittman arm to push the cross steer rod a little farther? Sorta afraid if I put a longer Pittman arm on it it won't be parallel with the tie rod anymore, and I don't want to introduce any bump steer. Stock Lincoln beam axle, cross rod tie rod end bolted right to Pittman arm after enlarging the hole just a bit, same radius turning both directions, shorter than it was. I can get used to it, just wondering if I can improve it a bit? Thanks
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 49,861

    squirrel
    Member

    As long as the drag link (cross steer rod) is mostly parallel to the ground, it should not add any bump steer.
     
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  3. alanp561
    Joined: Oct 1, 2017
    Posts: 1,867

    alanp561
    ALLIANCE MEMBER

    It's not going to take a heck of a lot more length on the Pittman to tighten up the turning radius. A quarter of an inch will make a lot of difference.
     
  4. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 8,936

    mgtstumpy
    Member

    A short pitman arm has a narrower sweep (Arc of travel) than a longer pitman arm. Will a longer arm work with your setup without fouling and interfering with geometry?
    [​IMG] Arc.jpg
    Exaggerated example
     
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  5. indyjps
    Joined: Feb 21, 2007
    Posts: 4,406

    indyjps
    Member

    If youve ever driven a third gen camaro or firebird the turning radius is not great anyway.
    From memory an 82-93 S10 2wd steering box should bolt in place of a third gen box. Please verify its been a while since I looked at all the options.

    Third gen boxes had an optional fast ratio 12.7 to 1. Standard third gen boxes were a slower ratio, S10 is 14 to 1 with more travel.

    Third gen f body and S10 Should all be saginaw 800 boxes, there are differences over the generations, when they switched from SAE to metric lines.
     
  6. Mr48chev
    Joined: Dec 28, 2007
    Posts: 30,059

    Mr48chev
    ALLIANCE MEMBER

    You are on the right track but you also need the idler arm that matches the pitman arm length wise.
     
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  7. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,744

    gimpyshotrods
    ALLIANCE MEMBER

    He's using it for cross-steer on a beam axle.
     
  8. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,744

    gimpyshotrods
    ALLIANCE MEMBER

    Not sure what the center-to-center length of your current pitman arm is, but this is a possible substitute:
    https://www.ihpartsamerica.com/stor...ySlJCfKUjDbv0Z8VnzikcD-HMKfBJLthoCjVgQAvD_BwE
     
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  9. nobby
    Joined: Jan 8, 2006
    Posts: 722

    nobby
    Member

    s10 is i think 6 inches on centres -
    jeep grand cherokee
    1. has the same clocked straight ahead splines
    2. has a similar drop
    3. is longer i think
    4. has a small taper for tie rod - I.E. can be enlarged

    when you buy a pitman arm and get the old packet, it listst the lengths on the in a check box type affair
    I am pretty confident that 6'' on centres is the starting point.
    I have sold the grand cherokee one i had, but am sure it was longer.


    ooh, a 70-71 pontiac full size pitman is 6 and an 1/8
    fits the power saginaw
    has the same early ford taper at 1.5 inches per foot
    is the input length on the double eye side steering arm 7 inches?
    i say that because with a 37 spindle, 6 1/8 pitman and a quick 800 box - its perfect
    1 1/4 turns lock to lock and quick
     
    Last edited: Aug 5, 2021
  10. BamaMav
    Joined: Jun 19, 2011
    Posts: 5,112

    BamaMav
    Member
    from Berry, AL

    I'll have to do some measuring. I started with the S10 box, but when I got it all hooked up it had hard spot just off center, so I went with the fire bird box which looks identical and swapped the Pittman arms because they were the same length instead of having to open up another one for the rod end.

    Sounds like I was correct, a longer arm should give more turning radius with a slower speed. Now to do some looking around....

    Thanks!
     
  11. squirrel
    Joined: Sep 23, 2004
    Posts: 49,861

    squirrel
    Member

    when you say "more" turning radius, do you mean "tighter" turning radius? Because "tighter" is "less".
     
  12. BamaMav
    Joined: Jun 19, 2011
    Posts: 5,112

    BamaMav
    Member
    from Berry, AL

    Tighter? Right now, it is so wide, I had to back up and go again to make a turn out of my yard that I should have been able to make in one swing. I guess I wasn't wording it correctly. It takes too big an area to turn, so I need to push the draglink farther to cut the wheels farther to close up the turning distance.

    Hope that makes sense!
     
    Last edited: Aug 5, 2021
  13. 1971BB427
    Joined: Mar 6, 2010
    Posts: 7,055

    1971BB427
    Member
    from Oregon

    Unless you went to a much longer arm, the geometry should not change. And length of the arm has no affect on what we refer to as bump steer.
    As the arm moves in an arc, it is always less than parallel to the tierod and axle. So starting out slightly longer means it might even be a bit better, not worse. I wouldn't be concerned about going as much as 2" longer, as long as the current drag link is parallel to the tierod now.
     
  14. nobby
    Joined: Jan 8, 2006
    Posts: 722

    nobby
    Member

    it may be that the box itself will only travel that far?
    i think i have seem 800 saginaw sector shafts with both 3 teeth and 5

    what traval at the spindle do you need to see so the nut lands on the spindle stop
    -is it about 2.5''

    if the box only goes 2'' then its no good awyway?
     
  15. BamaMav
    Joined: Jun 19, 2011
    Posts: 5,112

    BamaMav
    Member
    from Berry, AL

    A little update:

    I checked the pittman arm on the car, the one I took off the FBird box, and the original 47 one, all three are the same length. I haven't driven the car again except here in the yard, when I noticed it seemed to cut tighter to the right than the left. This afternoon, I was taking my steering wheel off to center the spokes, and after I did that, I did a left from center and a right from center turn, and found out I have 1 1/4 turns left from center, and 1 3/4 turns right from center. Egg on face!

    Apparently, I didn't get the box centered when I put the pittman arm on. Don't know if I moved it a smidge, or just missed getting it centered. Going to take the pittman back off when I get a chance and see if the splines will allow it to mount centered, then adjust the cross link to fit.
     
  16. Canuck
    Joined: Jan 4, 2002
    Posts: 1,086

    Canuck
    Member

    Can always try your original Ford arm, I think they are the same shaft and spline as the GM arms, splines might be at a little bit different angle.

    Steering stops inside the box may be shortening your radius, maybe a earlier box housing could be utilized to get a larger turning radius.?
     
  17. dalesnyder
    Joined: Feb 6, 2008
    Posts: 476

    dalesnyder
    Member

    When they changed to to o ring lines they also changed the flat spot where the steering rag joint goes. I had to grind a new flat to align the box correctly. If you just move the steering wheel then the turn signal cam does not self cancel correctly.
     
  18. BamaMav
    Joined: Jun 19, 2011
    Posts: 5,112

    BamaMav
    Member
    from Berry, AL

    Good to know, may try that. Do they have the large flat spot in the splines like the GM box?

    I'm not worried about that end, I'm using a U Joint so it can be placed anywhere. Wondering about the flat spot on the pittman arm end if it will allow me to reposition it.
     
  19. Canuck
    Joined: Jan 4, 2002
    Posts: 1,086

    Canuck
    Member

    Some of my notes from years ago, nothing verified. Check comments about internal stops.

    - 1982 or 86 to 92 Comaro Z-28/firebird Trans-AM are 2 turns (12:1) lock to lock, Use original end cap to get the right stops on 2 turn boxes to decrease turning radius.
    - Later model boxes (1980 and up) use “O” rings instead of flared input and output lines.
    - Later model internals can be swapped into early boxes to eliminate problems with line fittings and stops or pump can be modified by changing outlet valve (this requires verification) or swapped to accept "O" ring hosed.
     
  20. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,744

    gimpyshotrods
    ALLIANCE MEMBER

    The double-wide splines inside the Pitman arm hole can be eliminated with a triangle file. That will give you 360º of freedom, and more possibilities for interchange.
     
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  21. BamaMav
    Joined: Jun 19, 2011
    Posts: 5,112

    BamaMav
    Member
    from Berry, AL

    Thanks Gimpy! That was something I couldn't remember fully, I was thinking there were a wide spline either on the box or arm or both. I need to move the pittman about 1/4 turn to have an equal 1.5 turns each direction.

    I need to pick up a triangle file and give the hole some loving passes.....
    Then hope I have enough adjustment on the tie rod ends to connect back.
     
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  22. gimpyshotrods
    Joined: May 20, 2009
    Posts: 18,744

    gimpyshotrods
    ALLIANCE MEMBER

    The sticky-outy wide bit (technical term) is always on the pitman arm. You just need to manually cut your own splines.

    Even if you go a little past it's fine, there are more than enough machine cut ones.
     
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  23. BamaMav
    Joined: Jun 19, 2011
    Posts: 5,112

    BamaMav
    Member
    from Berry, AL

    Took a look at it this morning, discovered some hack had welded the nut and the arm to the box shaft! Some people need their thumbs cut off!

    I looked at my other GM arm, I see what you're saying on the wide splines, one on each side, 180 degrees apart. I'll practice on it before I take the one on the car off and recut it. Thanks again!

    And I like that technical term from a technician, LOL!
     
  24. topher5150
    Joined: Feb 10, 2017
    Posts: 2,520

    topher5150
    Member

    So the original 47 pitman arm will fit a GM box? Will it hit the tie rod?
     

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