trans quick shift

Discussion in 'GM Powertrain' started by grumpy old man, Mar 11, 2010.

  1. I went temporarily brain dead and was cranking the engine with the coil wire out. This stupid stunt fried the ignition module. I made a trip to the parts store purchased a new module and the engine started right up. Now the trans is quick shifting, third gear before you clear the intersection. If you shift the trans manually it works fine. I obviously made something in the electronics mad but have no idea what. The scan tool shows all systems normal and no codes. Anyone have any ideas?
  2. cobra2end

    cobra2end Rockstar 100 Posts

    I had a 1991 6.2 that would shift hard. i took the battery cables off and it shifted fine i left them off for just a few mins was all. might work for you too. Not sure if it resets computer or not.
  3. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    What's happening is your PCM thinks your transfer case is in 4 Low. When in 4 Low a ground signal is sent to the PCM and the shift strategy is is sped up to match the low range. When this wire is grounded in 2WD the trans shifts way too fast.
    Try unplugging the battery and the ECM. If the problem still persists you can clip the wire at the PCM which will correct the problem.

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