Duramax and Allison

[KAB]

There is a known problem when an aftermarket heater is added:

December, 2006

Dear Valued General Motors Customer:

Subject:
Added after market transmission sump heaters used in:

• 2006 Chevrolet Silverado 2500 (3/4 Ton) and 3500 (1 Ton)


• 2006 GMC Sierra 2500 (3/4 Ton) and 3500 (1 Ton)


• 2007 Chevrolet Silverado Classic 2500 (3/4 Ton) and 3500 (1 Ton)


• 2007 GMC Sierra Classic 2500 (3/4 Ton) and 3500 (1 Ton)


Equipped with 6.6L Duramax™ Diesel Engine (VINs D, 2 -- RPO's LBZ, LLY)

and Allison® LCT 1000 (RPO MW7) Six Speed Automatic Transmission

General Motors is committed to customer satisfaction and we want you to have absolute confidence in our products. Our records indicate you may currently own one of the vehicles listed above. This letter is to advise you of a potential product concern, which could occur if an aftermarket transmission sump heater has been added to your vehicle.

If an aftermarket transmission sump heater has been added to your vehicle, it may be susceptible to transmission failure when all of the following conditions exist:

• The vehicle is exposed to -40°C (-40°F) for more than 8 continuous hours (cold soak)

• An aftermarket transmission sump heater has been added to the vehicle

• The aftermarket transmission sump heater is active

• The vehicle’s Elevated Idle Mode is engaged (refer to Owner’s Manual for details to determine if your vehicle has this feature engaged)

When a vehicle has been exposed to this extreme cold temperature for an extended period of time, the fluids become very thick. An aftermarket transmission sump heater warms the transmission fluid in the transmission, allowing it to operate. However, since the aftermarket heater does not warm all the transmission fluid, such as that fluid located in the cooler lines and transmission oil cooler located in the radiator, that fluid remains very thick and cannot flow. When the Elevated Idle Mode is engaged the transmission temperature could increase to a level that may cause damage to the transmission.

If you own one or more of the vehicles described above with an aftermarket transmission sump heater, we recommend you have the Transmission Control Module (TCM) recalibrated to accommodate the effect of the aftermarket sump heater and eliminate this potential over temperature concern. This recalibration is beneficial only on vehicles located in extreme cold climates with all the conditions listed above. Disabling the Elevated Idle Mode is an interim action that will protect the transmission prior to the TCM recalibration being performed. Elevated Idle can be engaged or disengaged using the driver information center controls or by the following method.

Turn the ignition to RUN, with the engine off.
Press the accelerator pedal to the floor and hold while quickly pressing the brake pedal three times in less than eight seconds.
Release the accelerator pedal and start the engine.
Please contact your local GM Dealership at your earliest convenience and reference this letter when scheduling an appointment. Since this recalibration is only necessary to accommodate the effect of an added aftermarket transmission sump heater, you would be responsible for the cost to recalibrate the TCM. Your dealer can advise you of the cost to perform this service.

Damages resulting from aftermarket modifications are not covered by your vehicle’s GM Warranty.

We regret any inconvenience this may cause; however, we are making this correction available in the interest of your continued satisfaction with General Motors products.

 

[Egon]

That is interesting KAB.

I do not know if the trucks mentioned had trasmission heaters.

 

[MossRoad]

...You will find that at temperatures around the -40 C/F things get a little more tense than zero degrees fahrenheit!...

The trouble with him was that he was without imagination. He was quick and alert in the things of life, but only in the things, and not in the significances. Fifty degrees below zero meant eighty-odd degrees of frost. Such fact impressed him as being cold and uncomfortable, and that was all. It did not lead him to meditate upon his frailty as a creature of temperature, and upon man's frailty in general, able only to live within certain narrow limits of heat and cold; and from there on it did not lead him to the conjectural field of immortality and man's place in the universe. Fifty degrees below zero stood for a bite of frost that hurt and that must be guarded against by the use of mittens, ear-flaps, warm moccasins, and thick socks. Fifty degrees below zero was to him just precisely fifty degrees below zero. That there should be anything more to it than that was a thought that never entered his head.

 

[Egon]

Ah so and so it was That on "The Marge of Lake Labarge We Cremated Sam McGee".

And I have stood on the Marge of Lake Labarge! but only in the summer!

 

[Zick]

Here is an on going discussion about the same thing at the Diesel Place.
Allison Rumour - Diesel Place

That's not your thread is it Egon?

 

[crbr]

My friends observations have merit. He watched them come in on the back of tow trucks. I recall he mentioned four in a two hour period. And yup he does tell the truth.



You will find that at temperatures around the -40 C/F things get a little more tense than zero degrees fahrenheit!

Have you ever been in cold weather service???

Right..... Here's a message for your source... What he sees on the rollbacks is not what makes the world go around, although one has the choice of belief...

I started out with the LB7 in 2001. Go figure...


Here's the scoop. Take it or leave it.

It is not the Allison, but GM has regionally recalled the air pipe connected to the Mass airflow sensor & redesigned it. The northern tier dealers said they gets 2-3 calls a day. It turns out a sensor is freezing up inside the pipe & GM will replace the pipe & sensor with a new design. The frozen sensor causes the truck to go into "limp mode" which feels as though the tranny is having issues.

GM will repair according to "region" I was told. (I assume this means if you are in a cold environment).


Owning a diesel and watching rollbacks .... I'm just saying....


....

 

[KAB]

CRBR - Look at my post about the problem. That is directly from GM.
I could not find any regional recalls for any of the items that you listed.


It has just been expanded to the new body styles for 07 and 08.

Kurt

 

[TCBoomer]

Right..... Here's a message for your source... What he sees on the rollbacks is not what makes the world go around, although one has the choice of belief...

I started out with the LB7 in 2001. Go figure...


Here's the scoop. Take it or leave it.

It is not the Allison, but GM has regionally recalled the air pipe connected to the Mass airflow sensor & redesigned it. The northern tier dealers said they gets 2-3 calls a day. It turns out a sensor is freezing up inside the pipe & GM will replace the pipe & sensor with a new design. The frozen sensor causes the truck to go into "limp mode" which feels as though the tranny is having issues.

GM will repair according to "region" I was told. (I assume this means if you are in a cold environment).


Owning a diesel and watching rollbacks .... I'm just saying....


....

FWIW...I'll leave it

KAB is correct with what he posted. In addition, this -transmission- issue does not apply to 05 and older due to a different cooler function.

Here's something straight from the horses mouth ...a copy of the letter I received

December 2007
Dear General Motors Customer:

This letter is to inform you of a condition that can occur in your 2006-08 Chevrolet Silverado HD or GMC Sierra pickup truck when air temperatures fall below minus 40 degrees (-40ｰ C/F) (excluding wind chill). If you do not operate nor expect to park your Silverado or Sierra outside for extended periods in far northern or western plains regions where temperatures may fall below -40ｰ C/F, no action is necessary.

We have learned that your vehicle may have limited or no transmission fluid (oil) flow through the transmission oil cooler after sitting for an extended period of time, such as overnight, during extreme cold temperatures -40 ｰF or ｰC or less. If the "Elevated Idle Mode" cabin heater performance option is operative and the engine is allowed to idle for an extended period of 15 to 30 minutes while cooler flow is limited, the transmission fluid may overheat, resulting in transmission damage, and subsequent failure.

Your satisfaction with your 2006-08 Chevrolet Silverado HD or GMC Sierra HD pick up truck is very important to us, so we are announcing a program to prevent this condition or, if it has occurred, to fix it.

What We Will Do: To prevent this condition from occurring, your GM dealer will reprogram the Transmission Control Module (TCM). This service will be performed for you at no charge until February 28, 2009.