70 Z28 Leaf Springs

Discussion in 'Original Drivetrain Topic' started by camaro gold z28, Nov 3, 2007.

  1. M21RSZ28

    M21RSZ28 Veteran Member

    548
    2
    Mar 9, 2006
    1970 Z28 rear leaf springs

    Camaro Gold

    During the 1970 assembly line production for the Z28 Camaro two different rear leaf springs were used, the early production Z28 rear leaf springs used a lower spring rate compared to the higher spring rate used on the later production 70 Z28 rear leaf springs.

    Both early and late 70 Z28 rear leaf springs were five leaf and the four leaf springs were used on standard Camaros without SS or Z28

    The 1970 Z28 Camaro 1st design rear leaf spring was used thru March of 1970 at the Van Nuys Assembly Plant. I do not have a date for the Norwood Plant as to when the 1st design spring was no longer used in production

    The 1st design spring gave the early 1970 Z28 Camaros a lower ride height compared to the later production Z28 Camaros that used the 2nd design 3992580 rear leaf springs, which gave the later Z28 Camaros a higher ride height. The higher ride height is what most people are more familiar with.

    The change over to the 2nd design rear leaf spring with the higher spring rate that gave the later production 70 Z28 Camaros the higher ride height occurred at the Van Nuys Plant around the end of March 1970 or 1st week of April 1970 as verified by a friends 1970 Z28 Camaro build sheet dated April 3rd 1970 with the 2nd design spring code listed in box 14

    I have a copy of his 1970 Camaro build sheet from the Van Nuys Plant dated 04-03 for this April 3rd built 1970 Z28 Camaro with the 1st design spring code printed in box 14. The original 1st design spring code was then crossed out by hand and the 2nd design two letter spring code was hand written above the old two letter code.

    This hand written change was made to the original top copy of this build sheet at the Van Nuys Plant office, which left the hand written information looking like a carbon copy print on this copy, one of at least 4 copies used on the assembly line.

    I do not have the exact date when the change occurred on the assembly lines at either plant. The actual date would vary depending on when the supply of 1st design springs were exhausted at the Norwood and Van Nuys Assembly Plants

    The change over from 1st design to 2nd design rear leaf springs on 1970 Z28 Camaros can be found by comparing January-March and April- July Norwood broadcast sheets or Van Nuys build sheets

    The 1971 Z28 Camaro continued to use the 2nd design 3992580 rear leaf spring with the higher spring rate, which can be confirmed by a Broadcast Sheet or a Van Nuys Build Sheet from a 1971 Z28. The rear spring is listed in box 16 on the 1971 Camaro build sheet and will Have the same two letter code used on the later 1970 Z28 Camaros with the 2nd design 3992580 leaf spring

    1970 Z28 Camaros built at the Van Nuys Plants after March 1970 (Norwood date unknown) and all 1971 Z28 Camaros used the 2nd design 3992580 rear leaf springs, which would give the later 1970 Z28 Camaros and all 1971 Z28 Camaros the same ride height

    Original 1st and 2nd design Z28 Camaro rear leaf springs used on the Assembly Line were stamped with the GM part number and a two letter identification code using a Stencil with white dye, the two letter identification code was listed on the 1970 Camaro broadcast sheet and in the 1970 Camaro Build Sheet in box 14

    The GM part number and the two letter identification code is stamped with a dye on top of the rear leaf spring between the rear spring/shock bracket back to the first clamp used to secure the leaf springs together, the emergency brake cable runs along the leaf spring in this location. Most often the leaf spring is either covered in heavy rust or layers of paint hiding the stenciled part number and two letter code

    The 1970 Camaro Packet information dated February 1970 offered by Chevrolet’s Customer Service Center lists the 1970 Camaro rear leaf spring chart in the Chassis Section on page 6 under Rear Axle And Suspension. The Rear Spring Chart lists the 1st Design Spring as 481992 PK, however this is not the correct part number or two letter code used on the Assembly Line for the 1st design spring and the 2nd design 3992580 rear leaf spring is not listed
    in this chart

    As with the rest of the 1970 Camaro packet information and the 1970 Camaro AMA Specification Sheets both dated February 1970, these early publications have some early dated information that is either incomplete or incorrect, with various changes being made thru out the 1970 Camaro production year that was not added to those publications

    A monthly publication provided by Chevrolet’s Service Department, which was sent to Chevrolet Dealerships called The Chevrolet Service News dated July 1970 has listed on page 16 a 1970 Camaro Service Spring Revision Chart with the correct 2nd design 3992580 rear leaf spring listed for the 1970 Z28 Camaro

    There is nothing like original parts, if you still have your original rear leaf springs use them, clean them up carefully and try to save the Stencil part number and two letter code on the spring and then have your original springs re-arched

    Your best bet is to have your original rear springs re-arched by a business that specializes in leaf Springs; Diesel truck springs are re-arched several times over the lifetime of the spring. Re-arching the leaf spring will return the spring back to its correct arch and will return your car to the correct factory ride height. Look for a business that re-arch diesel truck springs; some will also re-arch automotive leaf springs and will have leaf spring charts with the correct spring arch by year and model application

    M21RSZ28
     
    Last edited: Nov 5, 2007
  2. Smokin70SS

    Smokin70SS Veteran Member Lifetime Gold Member

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    Apr 13, 2002
    Pasadena,CA
    If you just put them in give them a little time. They should break in after a while. The fastest way to break them in is driving the car and loading them up by launching with them ;)

    Once they've settled you can assess the ride height situation and see if they need to be re arched.

    Also, Budz, is right. Always leave the leaf spring bolts loose and then tighten once the car is on the ground.
     
  3. citrusz

    citrusz Veteran Member

    447
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    Mar 10, 2005
    Long Island, NY
    Thanks M21RSZ28,

    You just cleared up that leaf spring issue with my 70 Z Van Nuys build. Box 14 is crossed out and DY is hand written in. Also found and put back the DY on the leaf springs. You mention a stencil marking? DY was the only marking I uncovered. Do you have pictures of these other markings?
     
  4. camaro gold z28

    camaro gold z28 Veteran Member

    343
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    Sep 21, 2004
    severn, maryland
    Thank you for the info on the leaf springs, very good.
    The car I am restoring now did not have the original leaf springs.
    But my last project did. Here is a pic of the spring. It shows the part number as you stated. Not seen in the photo. there does appear to be a "DY" after the number.Part No is 3992580. Also, note the original black coating on the spring preserved under the perch rubber pads.

    [​IMG]
     
  5. White81Z

    White81Z Veteran Member

    1,174
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    Nov 17, 2004
    NY
    My survivor 1970 Camaro, 307, T350 has/had five leaf rear springs. They have since been replaced with the correct replacements because they were broken and unsafe. Picture shows the original springs.

    For what it's work the springs fit perfectly and the ride height was corrected.

    Rick H.

    Before
    [​IMG]

    After
    [​IMG]
     
  6. flowjoe

    flowjoe Moderator Staff Member Lifetime Gold Member

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    Feb 7, 2006
    SoCal
    Rick, are those Eaton springs? Or??
     
  7. White81Z

    White81Z Veteran Member

    1,174
    0
    Nov 17, 2004
    NY
    Not sure of the brand but I know they are not Eaton's. I am on business travel and when I return I'll find out for you. I have another set that are going on my '70 Z/28. They fit great and I plan on using them more often.

    Rick H.
     
  8. M21RSZ28

    M21RSZ28 Veteran Member

    548
    2
    Mar 9, 2006
    Stand Corrected -Thanks

     
    Last edited: Nov 5, 2007
  9. Budz

    Budz Veteran Member Lifetime Gold Member

    2,944
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    Mar 17, 2002
    Ashburn, Va USA
    It appear's to me that you don't miss very much.......;)
     
  10. M21RSZ28

    M21RSZ28 Veteran Member

    548
    2
    Mar 9, 2006

    Thanks Buddy,

    I try to be as accurate as possible with just the facts and keep my opnions to my self, opinions are like elbows and ........ will you know, everyone has at least one.

    M21RSZ28
     

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