Powerglide is all power and no glide.

Discussion in 'The "Juice Box"' started by Max Damage, Oct 25, 2020.

  1. Max Damage

    Max Damage I'm working on it!

    The Super Turbine 300 in my 1968 GS Cal isn't shifting. Apologies for calling it a Powerglide! It stays in low...

    It hasn't been serviced in a while, so I suppose that is first.

    Also, I did have the carb off and rebuilt, could I have messed something up there?

    Thanks for your thoughts and ideas.
     
    Last edited: Oct 26, 2020
  2. Bens99gtp

    Bens99gtp Well-Known Member

    Does it have reverse
     
  3. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    Stop calling your st300 a powerglide and maybe it'll start to behave!
     
    TrunkMonkey likes this.
  4. Brad Conley

    Brad Conley RIP Staff Member

    Your transmission is zero relation to a powerglide...it's a Super Turbine 300.
     
    TrunkMonkey likes this.
  5. bostoncat68

    bostoncat68 Platinum Level Contributor

    Well now that we have cleared up this egregious use of Chevrolet's nomenclature for their 2-speed transmission.... Let's stir the pot and refer to it as a Jetaway (which it is - the st 300 Olds' version)... Any chance you disconnected the vacuum modulator?? That might cause a very late shift but it should shift eventually?
     
  6. Bens99gtp

    Bens99gtp Well-Known Member

    The band i believe is what applies to get low, the rear clutch gives 2nd, the front clutch gives reverse. If it never feels like it tried to shift......could be governor not working or a stuck shift valve
     
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member


    ALWAYS check the simple things first. First thing to do is check the vacuum modulator vacuum connection. If it is leaking or disconnected, the transmission will think you are at WOT, and it won't shift, unless you wind it all the way out at WOT.

    Since you had the carburetor off, you might have disturbed the vacuum line at the intake manifold.
     
    Last edited: Oct 26, 2020
    bostoncat68 likes this.
  8. Max Damage

    Max Damage I'm working on it!

    Ok! I just discovered this by looking in the Chassis manual. My apologies to the ST300 and it's supporters (including me).

    I stupidly assumed that because it's a two speed that it was a power glide. Live and learn.
    Yes, Reverse works fine.
     
    Last edited: Oct 26, 2020
  9. Max Damage

    Max Damage I'm working on it!

    I am learning, sorry I didn't do my homework first.
     
  10. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Never mind about that, check the vacuum line.:)
     
  11. Max Damage

    Max Damage I'm working on it!

    OK, Now that I properly address my transmission as a Super Turbine 300, it works perfectly! Actually, the vacuum hosing all looked good, and the fluid level is correct still nice and bright red.

    However I discovered the kick down switch on the gas pedal wasn't returning to it's off position (spring?). Manually sliding this off, allows the transmission to shift as intended.

    So, is a kick down switch for a 1968 buick 350/ST300 a normal auto parts store part? Thanks for all of your patience and help.
     
  12. telriv

    telriv Founders Club Member

    The modulator on the trans. is vauum operated. IF the hose feel off it won't shift until the overnor says so.
    ALSO IF you look at the switch it can & does come apart & clean it. Could be all that's needed.
     
  13. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    That's the other thing, constant 12 volts to the kick down connection will prevent an upshift. That was your problem. Same switch as the ST/THM400. GM Part number 1242101. ToddsGS should have it.

    https://www.stage1restoration.com/product/switch-kick-down-switch/

    https://www.ebay.com/i/271949920322...kmOJrGwUuEH9uS3RptlF26wphTa-0LNsaArUJEALw_wcB
     
    Last edited: Oct 26, 2020
  14. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    Easy fix. You can drive it without the switch until the replacement comes in.
     
  15. Max Damage

    Max Damage I'm working on it!

    Right thank you guys! Larry, so convenient with the link, can you just pay for that too?
     
    bostoncat68 likes this.
  16. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member


    I could, are you destitute?:D:D
     
  17. Max Damage

    Max Damage I'm working on it!

    Thanks larry! I got it.
     

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