Transmission decode

Discussion in 'The "Juice Box"' started by ribuick, Jul 1, 2021.

  1. ribuick

    ribuick Well-Known Member

    Hello I need a little help trying to figure out a what, when, how. I have a BT code transmission in a 69 GS-400 Stage 1 convertible. I know that it should be a BB code for this car, but I have what I have. The caar has been in the family since 1970 and has never been in a shop for any trans problems. I am curious if this could be a factory or dealer replacement from the time of build until we bought this. Here are all of the numbers: the tag reads: on top: 68T 538, bottom: BT-68-233934. The stamp on the opposite side reads: 8H370386. I have never had any reason to think this was anything but a BB code trans. Any help is greatly appreciated.
     
  2. ribuick

    ribuick Well-Known Member

    As another note, the parts manual has this trans going into a 69 Riv with a 430ci. eng
     
  3. Duane

    Duane Member

    The vin number stamped into the trans is “8H370386” so the trans originally came out of a 1968 Flint built Buick.

    I believe the “BT” transmissions are for the big cars, so there is your answer.
    Duane
     
    BUQUICK likes this.
  4. BUQUICK

    BUQUICK I'm your huckleberry.

  5. Bens99gtp

    Bens99gtp Well-Known Member

    Most bt trans are switch pitch models. The several that I've had all were from big cars 430 and short shaft......but most took the older smaller od slipe yoke originally
     
  6. ribuick

    ribuick Well-Known Member

    Thank you all for your replies. Yes it definitely was replaced, when we bought the car in 1970 with 1600 miles, we were never told by that owner it had a replaced trans. We never had it in a trans shop. Would the factory or dealer done something like this swap for some reason? I have it out for a rebuild right now and have asked the rebuilder if he can let me know what it may have for internals, modulator, governor, gears, etc. It was always a stout trans and never gave a problem, just to all the power without a complaint. At least it came from the Flint plant, same as the car itself.
     
  7. pbr400

    pbr400 68GS400

    Any number of possibilities. The one thing that would be less likely is the dealer doing it. Any problem other then customer abuse should have been warranty work which would have been a factory service replacement trans. I guess the dealer could have said ‘GM won’t cover it but we’ll help you some out of good will’ and then put a used one in.
    Patrick
     
    Last edited: Jul 2, 2021
  8. BUQUICK

    BUQUICK I'm your huckleberry.

    I highly recommend that you upgrade the intermediate sprag since you have the transmission apart. This is the only part I was ever able to break in my 400 transmission with a relatively stock GS400 engine.

    upload_2021-7-2_11-47-23.png
     
  9. ribuick

    ribuick Well-Known Member

    I guess I will have to chalk this up to a mystery, since no records exist for these years. I will just enjoy putting some miles on it when I am done. The body and chassis went to the body shop yesterday.
     
  10. ribuick

    ribuick Well-Known Member

    Thank you, I will discuss the upgrade to the rebuilder. He may already have this in mind. He does all of my engine builders race transmissions. Highly recommended individual.
     

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