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  1. #1

    Default 700R4 Transmission identification question

    Hello, I am about to replace the transmission in my '83 K5 Blazer.

    this is a picture of the transmission that was in the truck:

    this is a picture of the transmission that I want to put in the truck. I noticed there is a difference in the upper left corner.

    Can anyone tell me what the difference is between these two transmissions? On the outside they both look like 700R4 transmissions.

    Thank you very much, Mark

  2. #2


    Over the 700R4's run, GM made modifications to the transmission to make it better. I don't recall what changes were made when, but a later-year transmission will of course have all the changes made up to that point. Additionally, if either transmission has been professionally rebuilt, the rebuilder may have applied all the changes to get it current. The serial number should be on the passenger side pan rail of the transmission. Here's a guide to help you decipher the serial number:

    1991 Chevy Suburban 1/2 ton 2WD w/ chevy SBC 350-3/4 ton drivetrain upgrade w/4.10 gears 200K miles
    2005 Saturn ION-2 Stock 277K miles
    1982 Bronco, 1993 Bronco (sold), 1971 M35A2 Deuce and a Half

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  3. #3
    Sr. Apprentice
    Join Date
    Mar 2014
    green river wy


    The one with the lube tube And the internal thermoster is I wanna say is 87 up can't really tell but the other one is pre 85 or 86 can't quite remember but totally different trans

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