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th350 problems

Discussion in 'The Garage' started by ryanxb, Aug 21, 2006.

  1. ryanxb

    ryanxb Newbie

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    i just bought a 77 K5 and the transmission won't shift from 2nd to 3rd. there isnt a problem getting into 1st or 2nd, but it just wont go in 3rd. there is a leak from the tranny pan, but i dont think that would cause it. if anyone has any ideas, please let me know. im completely lost. thanks.
     
  2. diesel4me

    diesel4me 1 ton status Premium Member

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    many causes...

    Anything from a low fluid level,to a bad modulator valve,or one with its vacuum hose disconnected, can keep it from up-shifting into 3rd..so can the detent cable being out of adjustment,or dissconected..if its too tight.it will hold the tranny in "passing gear"...burnt direct clutches can keep it from shifting up too..

    ...best way to diagnose it,if all external things check out, is to have a shop hook up a pressure test gauge to the ports on the side of the tranny case--they can check the pressure for first,second,and third,and reverse,just by removing a threaded plug,and installing the gauge in the port..any with low pressure probably have seals leaking or bad clutches..:crazy:
     
  3. wolfman

    wolfman Registered Member

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    Check the modulator valve first. It sticks out of the back of the trans and has a vacuum hose attached to it (or should). If the hose is attached check it all the way to the engine and make sure it is in good shape. Make sure you have vacuum with the engine running. If that is good replace the valve. It's around $12-$14 at the parts store. After that go with the other suggestions above.
     

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