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Tranny not shifting into 3rd. PLZ HELP

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by rebel222, Jun 22, 2002.

  1. rebel222

    rebel222 Registered Member

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    Location:
    Louisiana
    My th350 will not shift into third except for when it has been sitting overnight. It will shift probably twice if I go straight to the highway and then not againg for the whole day. PLEASE HELP.
     
  2. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Location:
    Sioux City, IA, USA
    Try it at wide open throttle yet?

    General Motors service manual says...

    1. Control Valve Assembly
    1a 2-3 shift train stuck
    b Valve body gasket- leaking, damaged, incorrectly installed

    2. Direct Clutch
    2a Pump hub - direct clutch oil seal rings - broken, missing
    b Clutch piston seals - missing, improperly assembled, cut, pistonal ball check stuck or missing.


    My guess would be a stuck shift valve. Now would a good time for a shift kit while you have the valve body off cleaning and examaning. All the valve body is a maze of passage through which tranny fluid passes. The pressure on the fluid is controlled by the governor and modulator. When the pressure reaches a certain point, it pushes open one of those little valves and operates the desired shift. Or something like that. I may be wrong, but I think that's the way it works.
     

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