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  1. #1

    Default Do I have a 4 or 5 speed Allison?

    After days of searching, I have decided the best thing to try is replacing the nsbu switch, but now I don't know for sure if I need a 4 or 5 speed switch. It would seem simple enough, I have p r n d 1 2 3, four speeds right? But it seems like most allisons are 5 or 6 in these trucks, so maybe I need to count OD as another speed? It is a 2002 with the 8.1. How can I tell for sure? Thanks

  2. #2
    Jr. Engineer racekid91's Avatar
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    Pretty sure Allison Transmissions were either 5 speeds, or 6 speeds. I think your's should be a 5 speed, I think the 6 speeds came out in like 2006 or 2007 for the Duramax's
    Last edited by racekid91; 02-06-2011 at 06:27 PM.

    1995 Chevy Tahoe

  3. #3

    Default

    Thanks, I think you're right. I guess the 4 spds are non-allison 2500 HDs. I ordered the 5 spd nsbu so hope it works. All the on-line research points to this. Thanks again

  4. #4
    Jr. Engineer racekid91's Avatar
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    Correct. If you had a 4 speed, it would be the 4L80E

  5. #5

    Default

    YEP, all the above ..lol

    1996 Suburban K3500 SLT DUALLY
    1988 Camaro RS 383 stroker LT1
    1992 32' Aero-tek Race Boat, 600 CI BBC
    WE CAN STICK A DIESEL IN ANYTHING
    SPECIALIZED IN CUSTOM CONVERSIONS OF ANY KIND
    Scott:glasses:

  6. #6

    Default

    maybe a dumb question. did the 8.1 come with the allison. I thought the allison was for the Duramax diesels and not the gasser. so If its the 8.1 it wouldnt it have the 4l80E correct? the 4l80E is a 4 speed
    David
    2004 Silverado 2500 Crew Cab 4x4, AMSOIL EA air filter, Granatelli MAF sensor, Throttle body spacer, Magnaflow exhaust (true dual to 2 in 1 out muffler), 6" ProComp lift (add a leaf and 5" superlift rear block), Bilstein shocks, 35's (Cooper Disoverer ST) and 4.10 gears, Rhino Liner, EGRUSA fender Flares and widow visors, extended stainless steel brake lines, firestone airbags w/onboard air compressor, Pioneer Avic X940BT navigation, Accel backup camera.
    http://www.gmtruckclub.com/forum/sho...Silverado-2500
    1960 Land Rover Series II 88
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  7. #7
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    I just looked at the sales literature that I got when I bought my 2003 2500hd D/A new in Aug of 2002. It shows the 5 spd allison as an option for the 8.1. The only problem I've had is the connector on the side of the TCU was not plugged in completly during assembly. This caused the trans to go into 3rd gear limp. Other than that the trans has been perfect.

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