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th 400 wont upshift. please help

Discussion in 'Chevy Trucks' started by mike s 88, Aug 19, 2004.

  1. mike s 88

    mike s 88 Junior Member
    Messages: 21

    anyone? 1988 will only shift at wide open throttle.
     
  2. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    Check your vaccuum line connections for leaks. Barring that, the governor could be stuck, but seems unlikely.
     
  3. mike s 88

    mike s 88 Junior Member
    Messages: 21

    thanks for the reply. governer is good vac is good. i have no clue. must be time to re build? thanks again, mike
     
  4. derekbroerse

    derekbroerse 2000 Club Member
    Messages: 2,377

    Did you confirm that you have actual vaccuum running thru the line and that nothing is plugged up? The vaccuum modulator could also be shot internally... maybe you can beg/borrow/steal one to swap in and try?

    If the tranny was not slipping or doing anything weird before this started, a rebuild seems like overkill. How does the fluid look anyways?
     
  5. Big Nate's Plowing

    Big Nate's Plowing PlowSite.com Addict
    Messages: 1,266

    my bet would be on the vac-modulator, about $15 at your local parts house and 10 min of your time