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Transmission Issue?

Discussion in 'Chevy Trucks' started by Eronningen, Jan 26, 2009.

  1. Eronningen

    Eronningen Senior Member
    Messages: 442

    I have a 2001 2500HD with the 8.1 gas, Alison transmission.
    I don't use it much in the winter but went to use it today and I put the gear selector in R and nothing. Tried many times. Put in D, 3,2, 1 and it moves foward but slips with power applied. Now I know its possible the tranny is smoked but are there any other scenarios possible??
    Last time it was used all worked fine with no slippage anywhere. What gives? If the tranny was going out wouldn't it slip for a few outings first?
    Tranny fluid is up and there is a check engine light on. Any ideas. 105,000 miles.
     
  2. BigDave12768

    BigDave12768 PlowSite.com Addict
    Messages: 1,446

    Could be a computer issue. Might need a reprogram. The Allison supposly learns the way the drive and adjusts to your driving habits. All controlled by a computer. So check for a code.
     
  3. t.i.b

    t.i.b Senior Member
    Messages: 140

    check engine lights a good thing, meens a scaner will read the code and tell u whats wrong. i would geuss range sellector switch.
     
  4. ticki2

    ticki2 Senior Member
    from NH
    Messages: 175

    Sometimes from sitting for a while , days, weeks , the torque converter can drain . Try letting it run for 10 or 15 min and go thru all the gears . Also try shutting off and restarting . Mine has done this before . It can also be the NSBU.
     
  5. Eronningen

    Eronningen Senior Member
    Messages: 442

    Interesting update. So I went down to shop tonight for a meeting. I was already planning on towing it in tomorrow but thought I'd start it and try it again. Si I did start it, put it in reverse and its solid, tried foward gears and their solid. I still have check engine light on but transmission is solid.
    I will take it in tomorrow and get the code read and report back my findings.

    Good news anyway for now.
     
  6. Eronningen

    Eronningen Senior Member
    Messages: 442

    What is NSBU?
     
  7. BigDave12768

    BigDave12768 PlowSite.com Addict
    Messages: 1,446

    if your torque convertor is draining down thats a sign of a bad TC and you tranny will be going soon. But I personally wouldnt run out and fix it since you will probably have to rebuild whole thing. So drive it till it blows
     
  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Not on an Allison it isn't.

    The '01-'02 Allison equipped trucks were well known for a TC drain back valve issue after a prolonged period of no use that was corrected long ago by a TSB...sounds like your truck never got the updated TC valve.

    Second likey cause would be the NSBU switch.

    But regarless yes you first need to scan it..your first code will be a P0700...it's the rest that matter.
     
  9. Philbilly2

    Philbilly2 2000 Club Member
    Messages: 2,566

    B&B, you I swear you beat me to every question I can answer. Right on the the drain back valve.
     
  10. Philbilly2

    Philbilly2 2000 Club Member
    Messages: 2,566

    NSBU is the Neutral Saftey Backup Switch.

    It is the ******* of the Allison tranny. Many of the problems that happen with the Allision 1000 start and stop with the NSBU switch.

    It is a small box on the drivers side of the tranny, behind the front drive shaft (4wd models) with the shift linkage going into it. Either tan or black in color. And one or two wiring harnesses plugging into it.

    Good news is that it is under $100 part, and can be changed in your driveway with 2 wrenches.
     
    Last edited: Jan 27, 2009
  11. Eronningen

    Eronningen Senior Member
    Messages: 442

    Final update. I took it in today. They plugged it in. Best they could tell it was the torque converter drained out on me. They suggested just leave it and not worry. Try to start the truck a little more often.
     
  12. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    If it is a drain back issue then yes it isn't a required fix...it won't hurt a thing to run it as is. More of a minor inconvenience than anything. A few minutes of warm up time and you'll never even know it does it.
     
  13. ticki2

    ticki2 Senior Member
    from NH
    Messages: 175

    It happens to some of the dodges too , if they sit for a long time.
    also keep an eye on thet tranny , not sure if they changed it but on my '94 I found out that it doesn't pump on park or reverse , only in gear or nuetral . A Trango shift kit will fix it.