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Allison tranny problems

Discussion in 'GM Powertrain' started by sr71, Mar 13, 2010.

  1. sr71

    sr71 New Member

    I have a 2001 Silverado 2500 HD with the allison 5 speed. Today after running fine it just seemed to go belly up. It does not show what gear I'm in on the dash gear indicator and will not shift into gear properly. If I shift to first and then start shifting up manually it seems to work. Could this be the neut safety/ backup switch or a fliud problem 58k on the odo.
  2. KidHauler

    KidHauler Epic Member 5+ Years 500 Posts

    It sounds electrical to me. Were you casual driving, or something different?

    I don't have much experience with Little Alli, but with the dash out and no auto shift, it sounds like something came unplugged. I'd crawl underneath and look for loose plugs. Check for codes, too.

    Good luck,
  3. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    This is a very common problem on the Allison 1000. The NBSU switch goes bad. NBSU is the neutral safety switch. There's plenty of info on how to change it on the net. Just Google NBSU.

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