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  1. #1
    Join Date
    Aug 2014
    Location
    Holley, New York
    Posts
    13

    Default any difference in turbo 400 from different years and engines?

    Back in September, I purchased a very original 1969 Grand Prix. It has the original number matching 400 engine and the original rear axle, though someone changed the gears. Through doing lots of research, I finally found that the original th-400 code PW was swapped out for a code PA transmission. The serial code plate is PA-77-66913, which from my research is a 1977 turbo 400 out of a LeMans/GrandPrix with a 301 engine. This transmission shifts through the gears very quickly, and doesn't like to downshift into 2nd when given a considerable amount of throttle. Are there any internal differences causing this, or does possibly the vacuum modulator on the side of the transmission need to be changed? I am looking for a set of original 3.23 gears to put back in the rear axle, so I want to make sure I have the tranny set right. Also, would the horsepower difference from the 301 to the 400 have anything to do with the operation of the tranny? Thanks

  2. #2
    Join Date
    Nov 2008
    Location
    Central New York
    Posts
    121

    Default

    I have a short tail 400 out of a '69 Grand Prix, shifted good when it was in the car and had the same gears. It's for sale if you're interested. Don't know much about what trans you have, but there should be a kick down switch that your gas pedal activates near the pedal, this is connected to a switch on the side of the 400 trans. I'd check to see if their there and connected first.
    Steve Naresky

  3. #3
    Join Date
    Aug 2014
    Location
    Holley, New York
    Posts
    13

    Default

    I might be interested in buying it. Can you verify the code on the tag and let me know how much your asking?

    Thanks Scott Hults

  4. #4
    Join Date
    Nov 2008
    Location
    Central New York
    Posts
    121

    Default

    I should be out in the barn this weekend, I'll snap some pics.
    Steve Naresky

  5. #5
    Join Date
    Nov 2008
    Location
    Central New York
    Posts
    121

    Default

    The tag is a yellow PW-69 81174. I have to move some more stuff to get some pics, it's still attached to my motor and stuffed under a bench.
    Steve Naresky

  6. #6
    Join Date
    Aug 2014
    Location
    Holley, New York
    Posts
    13

    Default

    Ok, thanks. my email is gtoguy389@gmail.com if you want to send the the pics directly to me when you get them.

  7. #7

    Default 400 tranny shift problems

    Hi after reading your shifting problem first if there was a bigger gear installed like a 411 or higher that will cause the trans to shift out a lot quicker for sure, and yes there are small changes in the various valve body springs for different years and engines also, But that stuff is not a big problem that a transgo shift kit will not cure in a heartbeat also replace that modulator and recheck the adjustment on the kickdown switch when the pedal is firmly on the floor that is when the switch should make or maybe a skoch sooner. Simple adjustment also to check the modulatior remove it and tap the little tube that the vacuume line hooks onto and see if any red tranny fluid seeps out, that means it is bad and also get a vacume guage and check the vacume at the modulator those steel lines from the engine down to the trans rust up inside over the years and restrict the vacuume going to the modulator. I have rebuilt way too many of those in another life and sometimes they will tick you off, hope this helps LEE!

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