GM Powerglide Question

Discussion in 'Other Rides' started by 4by4bygod, Feb 27, 2005.

  1. 4by4bygod

    4by4bygod 1/2 ton status

    Nov 13, 2003
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    With My Tinfoil Hat
    Hi All!

    Anybody have one of these trannys? I'm looking to find out what MPH is normal for the thing to shift out of first, at both part throttle cruising, and flooring the SOB.

    My dad is having difficulty with the one in his 66 chevelle. the thing shifts at 20 -25 mph regardless of how hard he mashes the gas. It will work fine if shifted manually. The car isn't driven very much.

    Any guesses as to what could be wrong, if anything?


  2. 70jimmy

    70jimmy 3/4 ton status Premium Member GMOTM Winner

    Mar 3, 2000
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    Released from Pueblo, told I belong in Southpark
    Vacuum modulator. It should be adjustable but if its been in there a while it might not hurt to replace it. Cheap and easy to do. Also a fluid and filter change never hurts. Mine had a threaded rod with a standard screwdriver slot on the end and your just twisted it to change the shift point.

    In my 66 pontiac I had the opposite if you mashed the gas it shifted about 95 mph and if you took it to about 75 then ease off the gas it would shift then you could back down to cruise at 55 or 65 or what ever.

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