ALLISON SLIPPING ON DOWNSHIFT

November 6, 2006

i recently bought a new pick up with an 8.1 and the allison six speed. it makes lots of noise when i put it in to and out of park as well as "slipping" 500 or so rpm's when downshifting from 5th to 4th. the temp never gets over 170 or so and the fluid has no discoloratoin or odd odor. I now have 3,000 miles on it and pulled my boat (9800 lbs.) today and it slipped on every downshift to 4th. is this normal for this transmission or do I have a problem?

GM-Tech · November 6, 2006

Following is some info concerning your noise shifting from park. I don't know about the slipping. We have not had to do one single repair on an allison since we began using it.

Subject: Allison LCT1000 Clunk Noise Shifting into Park or On Start Up in Park - keywords drive reverse shift #PIP3161A - (09/19/2006)

Models: 2001-2007 Chevrolet Silverado

2001-2007 GMC Sierra

Equipped with a Allison LCT1000 Transmission

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This PI is being superseded to add model years and conditions. Please discard PIT3161.

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

Condition/Concern:

Some trucks equipped with the Allison LCT1000 transmission may experience a clunk type noise on start up with the vehicle in park. Some trucks may also experience a clunk noise when shifting into park from reverse or a drive range. The condition may be intermittent.

The noise is a result of internal transmission clutch drag which is sufficient enough to load the output planetary carrier. The resultant load on the output planetary carrier can result in park pawl gear tooth impact against the park pawl and cause the clunk noise. The magnitude of the noise is dependent on the position of the park pawl gear relative to the park pawl.

Recommendation/Instructions:

This condition is considered to be an operating characteristic of the Allison LCT1000 transmission.

Repairs or replacement of the transmission will not correct this condition.

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.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

November 6, 2006

Following is some info concerning your noise shifting from park. I don't know about the slipping. We have not had to do one single repair on an allison since we began using it.

Subject: Allison LCT1000 Clunk Noise Shifting into Park or On Start Up in Park - keywords drive reverse shift #PIP3161A - (09/19/2006)

Models: 2001-2007 Chevrolet Silverado

2001-2007 GMC Sierra

Equipped with a Allison LCT1000 Transmission

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

This PI is being superseded to add model years and conditions. Please discard PIT3161.

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

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

Condition/Concern:

Some trucks equipped with the Allison LCT1000 transmission may experience a clunk type noise on start up with the vehicle in park. Some trucks may also experience a clunk noise when shifting into park from reverse or a drive range. The condition may be intermittent.

The noise is a result of internal transmission clutch drag which is sufficient enough to load the output planetary carrier. The resultant load on the output planetary carrier can result in park pawl gear tooth impact against the park pawl and cause the clunk noise. The magnitude of the noise is dependent on the position of the park pawl gear relative to the park pawl.

Recommendation/Instructions:

This condition is considered to be an operating characteristic of the Allison LCT1000 transmission.

Repairs or replacement of the transmission will not correct this condition.

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.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

© Copyright General Motors Corporation. All Rights Reserved.

<{POST_SNAPBACK}>

so it is just the way it is and not hurting anything, I assume there is no cure since there are no steps listed to correct, or are there things a dealer can do to make it better?

GM-Tech · November 6, 2006

are there things a dealer can do to make it better?

<{POST_SNAPBACK}>

Did you read the TSB? It says this is a normal operating characteristic and repairs or replacement of the transmission will not correct this condition.

November 6, 2006

are there things a dealer can do to make it better?

<{POST_SNAPBACK}>

Did you read the TSB? It says this is a normal operating characteristic and repairs or replacement of the transmission will not correct this condition.

<{POST_SNAPBACK}>

yes, i did read it, also where it stated that to follow the corrective procedures completely one at a time and if it fixed the problem then no additional procedures needed to be followed, that is what had me confused.

GM-Tech · November 6, 2006

yes, i did read it, also where it stated that to follow the corrective procedures completely one at a time and if it fixed the problem then no additional procedures needed to be followed, that is what had me confused.

<{POST_SNAPBACK}>

Sorry, that's a standard disclaimer that's at the bottom of every one of those TSB's.