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Allison Trans problem

Discussion in 'Truck & Equipment Repair' started by Superior L & L, Dec 25, 2008.

  1. Superior L & L

    Superior L & L PlowSite Veteran
    from MI
    Messages: 3,041

    W have a allison trans in a chevy 4500. For the past couple of weeks the shifter has been acting up. Moving it from park to drive and the light under the D would not light up but the R would. Then every once in a while we would not have any reverse then five mins later it would work. When it does work it works great no grinding or weird stuff. then when we were plowing yesterday the driver called and said the truck would jump out of gear in reverse. This would happen about every third or fourth time he would put it in reverse. He would have to put it in park turn the truck off, restart it and it would be fine.

    It may still be under warrenty ? did the allisons have 5/100,000 on the 4500's. Called deal and they are not real helpful. Said they could check a module or two but would probably send it to allison in detroit and who knows when it would be back!

    Please help
  2. no lead

    no lead PlowSite.com Addict
    Messages: 1,308

    checked fluid im sure. grab a kreeper and inspect the linkage on the drivers side of the trans. is it free of packed snow and ice? does it have a hot shift pto or anything else trans related?
  3. JD Dave

    JD Dave PlowSite Fanatic
    Messages: 11,194

    Sounds like a NSBU (sp?) switch, easy fix and very common. On edit after reading your post again I think I'm wrong.
    Last edited: Dec 25, 2008
  4. Scottscape

    Scottscape Senior Member
    Messages: 662

    Had the same problem with a 2500 last year. Took it to a alison tranny specialist and he said its from switching into 4hi while moving?? hasnt happend since
  5. Superior L & L

    Superior L & L PlowSite Veteran
    from MI
    Messages: 3,041

    No 4wd in this puppy

    I will check linkage but Its kept in a heated shop and happened within 45 mins of going out. Not sure what hot shift pto is but it does have a buton on the dash that if you push it then it will only stay in like scond or something like that
  6. Superior L & L

    Superior L & L PlowSite Veteran
    from MI
    Messages: 3,041

    What is a NSBU?
  7. JD Dave

    JD Dave PlowSite Fanatic
    Messages: 11,194

    Well from what I gather, it's a switch on the side of the tranny that controls how your tranny shifts, when my first one went I thought the tranny was smoked but for around $250 I was back on the road. It is very a common and easy fix on an Allison. Go to DeiselPlace and search the Allison forum and you will find your answer.
  8. plowdog

    plowdog Member
    from MN
    Messages: 45

    Def. a neutral safety back-up switch. Went through that this summer, 15 min. job and your done. No reason they can't install while you wait.
  9. ServiceOnSite

    ServiceOnSite Senior Member
    Messages: 950

    small price to pay for having the best tranny. imo
  10. JD Dave

    JD Dave PlowSite Fanatic
    Messages: 11,194

    Thanks I will remember that from now on.:drinkup: