'70 Z-28 Manual Steering

Discussion in 'Original Drivetrain Topic' started by Mulsanne Blue, Jul 10, 2013.

  1. roeville

    roeville Veteran Member

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    It is a 4 bolt. I'm not sure if this is original to the car but it works fine so I've never messed with it.
     
  2. 70moneypit

    70moneypit Veteran Member

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    Very confusing into. That pitman arm is correct for any power steering optioned 1970 Camaro, according to the catalogs. It does not appear to be correct for a manual steering car, but maybe in the early part of the year they did not have all three different types?

    The early suffix coded "A" version of 3864881 must have been superceded by revision "B" by at least May. Of course, there could have been an overlap in usage of the older "A" and the newer "B", as it could have theoretically taken them a few weeks to use up all the "A"s in the bottom of a bin if "B"s were piled on top of them before the bin was completely empty.

    The fact that the actual basic numerical part number did not change (on either the part or in parts catalogs) would indicate it was a minor revision of the same design and the two versions are/were totally interchangeable.
     
    Last edited: Jul 13, 2013
  3. DCL70

    DCL70 Veteran Member

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    My 1938-1971 Chevrolet Price Schedule (March 1971) has a list of abbreviations on the 2nd page.

    GMT - Parts or Accessories stocked at General Motors Truck Division Warehouses.

    Did GM have their own foundry that made suspension parts for trucks and cars?
    Just an idea......

    Dave
     
  4. FlaJunkie

    FlaJunkie Veteran Member Lifetime Gold Member

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    I have read that they did have a truck parts foundry...I just never knew much more about it.

    So, looks like they made this pitman arm at a GM plant.

    I would still like to ask any other 70 Z28 owners with manual steering what their pitman arm part number is.

    I wonder what the specs are on the 3964877? A pic of one would be nice!
     
  5. DCL70

    DCL70 Veteran Member

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    Has anyone ever seen a Pitman arm with a "3964877" casting (or forging) number?
    The GM part number is generally not the same as the casting number but is some cases it is.

    Isn't it possible that the GM # 3964881 and GM # 3964877 Pitman arms are made from the same casting (or forging) with "3964881" as the casting (or forging) number?

    Is the hole size in the Pitman arm the same size for both the manual steering box and the power steering box?

    Is the hole size in the Pitman arm the same size for the different centerlinks?

    My 1990 TRW Chassis parts catalog (for 1979 & prior models) does not even list a Pitman arm for the 1970-1979 Camaro models as it is a "Non wear" item.

    The TRW #DS829 centerlink is listed for 1970-1971 Camaro models w/SHP 350 & P.S. and all 1974-1979 models. The TRW #DS830 centerlink is listed for 1970-1973 Camaro models w/P.S. (exc. SHP 350 and 1973 models w/AC.).

    My 1970 Chevrolet Parts Catalog (Oct. 1970) lists the following part numbers for the centerlink (aka "Relay Rod" in Gr. 6.870):
    3964873 - 1970 Camaro w/SHP 350 & 70 Camaro w/P.S.
    3964883 - 1970 Camaro (exc. P.S., SHP 350)

    My educated guess is the difference is just the centerlink (aka Relay Rod) length.

    Dave
     
    Last edited: Jul 14, 2013
  6. Gary S

    Gary S Administrator Lifetime Gold Member

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    My 4/70 car has an "E" version of the 3864881.
     
  7. Mulsanne Blue

    Mulsanne Blue Veteran Member

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    Top is the 3964883 for manual steering and the bottom is the 3964873 for power steering. Note the off-set difference at the pitman hookup. All manual steering use the 3964883 center link. The different off-sets evidently require different length pitman arms. So, here's my hypothesis: All p/s use the 3964881 arm, the manual uses the 3964851 arm with the 7809668 (cast no.) steering box, and the 3964877 with the 5679142 (cast no.) box. The 3964851/7809668 is used on manual non-HP cars, and the 3964877/5679142 is used on the manual Z-28's.

    The only manual steering untouched Z that I know of is clill's 1,100 mile car. Charlie, could you check to see which pitman arm is on yours? Should clear up some things :) .
    [​IMG]
     
  8. clill

    clill Veteran Member

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    I don't own it anymore.
     
  9. fdeluca532

    fdeluca532 Member

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    I have the manual steering center link. barely used was on car 1 summer to drag race. for sale 60.00 plus shipping
    Its a moog part
     
  10. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    What I've always suspected and seems to be confirmed by the Camaro Supplement to the Chassis and Overhaul Manual page 13 is that the Z28 had the same manual steering box as the 6 cylinder and only increased the steering ratio by using the long 3964881 pitman arm. This then necessitated the use of the power steering center link and its corresponding idler arm. This only applies to the Z28. So, to change from power steering to manual only requires locating a 6 cylinder power steering box and some workout time at the gym to beef up those arms.

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