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Thread: th400 has no first gear

  1. #1

    th400 has no first gear

    Hi all my th 400 out of my 74 buick electra seems to have no first gear. it has all the others even reverse but I have to wind it up a bit to 2nd gear speed for it to go. I was wondering what the likely culprits might be before I start digging into it.

  2. #2
    first things first:
    1 - transmission fluid level?
    2 - condition of fluid?
    3 - last time the trans filter was changed?

    beyond that, you might get lucky have a blocked fluid passage but there's a good chance the 1st gear clutch pack is shot.

    the TH-400 doesn't change a whole lot over the years so the 1975 Chassis Manual will apply.

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  3. #3
    Quote Originally Posted by bob k. mando View Post
    first things first:
    1 - transmission fluid level?
    2 - condition of fluid?
    3 - last time the trans filter was changed?

    beyond that, you might get lucky have a blocked fluid passage but there's a good chance the 1st gear clutch pack is shot.

    the TH-400 doesn't change a whole lot over the years so the 1975 Chassis Manual will apply.

    https://www.teambuick.com/reference/...ssis/index.php
    That all should be ok I just put a shift kit in it and then I started analyzing this cause before I just chocked it up to well the th 400 must be a dog of a tranny. Then searched around and others have praised it so I was like well something must not be right and even when I pulled up to the tranny shop for something else the tranny guy said it sounded like I had no first gear cause my electra is loud and gets attention. Would it really go bad even though it doesn't have many miles on it?? All the other gears seem to work fine just like first is nonexistent. even in reverse I have to wind it up a bit to move.

  4. #4
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    Pull the governor out and check it for damage. The weights may be binding or, the valve in the stem may be sticking. Clean it with carburetor cleaner, dip it in ATF and reinstall it. See if that helps.
    Larry

    1970 GS455 Stage1 Race weight 4025 lbs.
    TSP 470, 602 HP, 589 TQ
    MT headers, Gear Vendors Overdrive
    Best E.T. 11.54 Best MPH, 116.06
    1998 Riviera SC3800

  5. #5
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    Probably a stupid suggestion

    We had the same problem (I think) after an engine change. For us it was a really simple fix. The vacuum tube to the gearbox had a small rupture because of the rubber drying out. We just replaced it and no problems since.

    Disclaimer, I don't know much about transmissions, but it is a quick check, if the trans is similar to ours.

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