Tempermental Allison trans.
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Tempermental Allison trans.

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    Senior Member SS-55's Avatar
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    Question Tempermental Allison trans.

    I've got a 2002 2500HD with the 8.1L and Allison 5 speed. 120,000mi. Original owner. Really love this truck and plan on keeping it forever! Heres the issue, a couple times in the last month I have started it up and let it warm up for 5-10 minutes(approx. 35-45 degrees outside in the driveway). I go put it in reverse and the gear indicator just blinks and doesn't shift. Try to put it drive and it clunks pretty hard and requires throttle to nudge. Put the transfer case in and out of neutral, let the truck roll etc. The first time it got over it, eventually, shifted, ran perfect. The second time I had to give up. Came out the next day, a little warmer out, didn't let it warm up but let the rpm drop to 750ish, slipped right into gear. Haven't had an issue for a week, ten days. Any ideas as to what could be going on. I'm no expert on the workings of the Allisons. Maybe a shifting solenoid, temp. related? Fluid in tranny is full. Truck isn't chipped, pretty stock other than exhaust and intake. Any help would be appreciated.

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    Senior Member 74 HOWARD 21RC's Avatar
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    Default Shifty

    Hey ss-55 I have a 01 hd 2500 4x4 with a diesel.I have had the same problem twice.But when it did it,it was under warranty.The paper work said it was the gear selector on the trans where the shift cable goes down to the trans.The y replaced it twice on two differnt occasions and have not had that problem since.I guess for us older guys it is where the nuetral safety swith would have been.I would try and replace it but I think you need a adjustment tool to reset it.

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    "Try it Now!" Tahiti Boss21's Avatar
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    Quote Originally Posted by SS-55 View Post
    I've got a 2002 2500HD with the 8.1L and Allison 5 speed. 120,000mi. Original owner. Really love this truck and plan on keeping it forever! Heres the issue, a couple times in the last month I have started it up and let it warm up for 5-10 minutes(approx. 35-45 degrees outside in the driveway). I go put it in reverse and the gear indicator just blinks and doesn't shift. Try to put it drive and it clunks pretty hard and requires throttle to nudge. Put the transfer case in and out of neutral, let the truck roll etc. The first time it got over it, eventually, shifted, ran perfect. The second time I had to give up. Came out the next day, a little warmer out, didn't let it warm up but let the rpm drop to 750ish, slipped right into gear. Haven't had an issue for a week, ten days. Any ideas as to what could be going on. I'm no expert on the workings of the Allisons. Maybe a shifting solenoid, temp. related? Fluid in tranny is full. Truck isn't chipped, pretty stock other than exhaust and intake. Any help would be appreciated.
    You may want to call John Wood Automotive in Holtville CA...www.jwtt.com He's very very helpful over the phone, mainly a ford guy, but i've seen him do a couple of Allisons like nobody's business. He's usually there m-f before 2pm...he's very patient and polite on the phone..something you don't hear of much these days.
    1992 Eliminator Daytona 21'

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    Senior Member carreradude's Avatar
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    I have a 2004 gmc 4x4 2500HD with the allison and 8.1L. I too love it! I only have 40K on it with no probs. Mine has the K&N cold air, gibson headers, 3" spintec mufflers (true dual exhaust). It toatlly hauls ass!! I want to do the hypertech programmer on it. Good luck on your trans deal.

    On a side note....how much oil does your 8.1 use?? I have to add about 2-3 qts for 5000 miles. Thanks for any info.

    Mike

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    Senior Member SS-55's Avatar
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    Thanks 74 Howard, shifty is right. I guess no damage is taking place so I'll just go with it for now, unless someone else sheds a different light on it.

    CarreraDude, that sounds about right, between my 3,000mi service intervals I go through about a quart topping off occasionally. I also drive it with a pretty light foot trying in vain to get some kind of fuel mileage out of it, but the 500 cubes usually win out. Did you know they no longer put the 8.1 in 3/4 and 1 ton pickups? Collecters item baby!

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    Senior Member SS-55's Avatar
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    I appreciate the referal Tahiti, I just may have to call him

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    Senior Member carreradude's Avatar
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    Quote Originally Posted by SS-55 View Post
    Thanks 74 Howard, shifty is right. I guess no damage is taking place so I'll just go with it for now, unless someone else sheds a different light on it.

    CarreraDude, that sounds about right, between my 3,000mi service intervals I go through about a quart topping off occasionally. I also drive it with a pretty light foot trying in vain to get some kind of fuel mileage out of it, but the 500 cubes usually win out. Did you know they no longer put the 8.1 in 3/4 and 1 ton pickups? Collecters item baby!
    I think they stopped making them in 2006?? Do you have the instant mileage computer on your truck?? Mine says around 11-13 mpg at 60mph.
    It is funny, it only looses about 1-2 mpg when towing my 21 ft boat.
    Great power horse and you don't need to hunt for diesel.

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    "Try it Now!" Tahiti Boss21's Avatar
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    Quote Originally Posted by SS-55 View Post
    I appreciate the referal Tahiti, I just may have to call him
    let me know if he was of any help!
    1992 Eliminator Daytona 21'

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    #PIP4379A: Delayed Or No Drive And Or Delayed Or No Reverse With DTC P0701 - keywords P0751 P0756 P0761 P0843 P0848 P0873 P0877 delay harsh shift fluid pressure switch - (Jan 8, 2009)


    Subject: Delayed or No Drive And or Delayed or No Reverse With DTC P0701


    Models: 2007-2009 Chevrolet Silverado

    2003-2009 Chevrolet Kodiak

    2001-2007 Chevrolet Silverado Classic

    2007-2009 GMC Sierra

    2003-2009 GMC Topkick

    2001-2007 GMC Sierra Classic

    Equipped with The Allison LCT1000 Transmission RPO M74 or MW7




    --------------------------------------------------------------------------------

    This PI was superseded to update model years. Please discard PIP4379.


    --------------------------------------------------------------------------------

    The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

    Condition/Concern:
    Customer may comment on a delayed or no engagement into drive and or delayed or no engagement into reverse with DTC P0701 along with any or a combination of the following codes; P0751, P0756, P0761, P0843, P0848, P0873 or P0877.

    Recommendation/Instructions:
    P0701 indicates no or excessively low pump pressure as a result of a no prime or loss of prime condition within the transmission pump. When any of the above DTCs are accompanied by a P0701 begin troubleshooting with the SI for P0701 first. Be sure to follow all diagnostic steps. Engineering has been involved and investigated cases of P0701 codes.

    DTC P0701 can set by the following: fluid service/filter change, transmission service involving removing the pan, low fluid level caused by leaks, or after long periods of storage.

    Important: Replacement of the TCM will not likely correct a DTC P0701 or low main line pressure.

    Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

    Dare to be different, if it turns out great you can claim you planned it that way.

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    mo balls than $cents$ IMPATIENT 1's Avatar
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    could also be the prndl switch on the side of the tranny with the shifter shaft runnin thru it. see that more often than the frt pump issue. you'll have to have a heat gun to get the connectors loose from the prndl, their hotglued during assembly and you'll have to heat the outside up to make the connectors release.

    Dare to be different, if it turns out great you can claim you planned it that way.

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    Senior Member SS-55's Avatar
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    Quote Originally Posted by IMPATIENT 1 View Post
    DTC P0701 can set by the following: fluid service/filter change, transmission service involving removing the pan, low fluid level caused by leaks, or after long periods of storage.
    Awesome Impacient, really appreciate you posting this. Interesting because every time(twice) this has happened the truck had sat for a couple weeks i.e. loss of prime. It seemed like temperature was a contributor and now it makes sense that the cold, more dense fluid could have caused pump starvation. Gotta love the wide variety of info. available from fellow boaters on these boards Thanks again guys

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    Senior Member SS-55's Avatar
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    Quote Originally Posted by carreradude View Post
    I think they stopped making them in 2006?? Do you have the instant mileage computer on your truck?? Mine says around 11-13 mpg at 60mph.
    It is funny, it only looses about 1-2 mpg when towing my 21 ft boat.
    Great power horse and you don't need to hunt for diesel.
    No, I dont think it was an option yet in 02. I just have to do the math with a calculator. Have had Chevys with the fuel range, awesome feature. I also like resetting the trip/lifetime fuel mileage and seeing what I get on trips, sort of becomes a game.

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    mo balls than $cents$ IMPATIENT 1's Avatar
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    Quote Originally Posted by SS-55 View Post
    Awesome Impacient, really appreciate you posting this. Interesting because every time(twice) this has happened the truck had sat for a couple weeks i.e. loss of prime. It seemed like temperature was a contributor and now it makes sense that the cold, more dense fluid could have caused pump starvation. Gotta love the wide variety of info. available from fellow boaters on these boards Thanks again guys
    change the external filter on it , drain the trans pan(15mm drain plug)and pour in 6qts,start motor, check from there and fill it to half way between the "cold" and "hot". sounds like its just gumming up alil from sitting. glad to help.

    Dare to be different, if it turns out great you can claim you planned it that way.

    Jetboatperformance.com

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