PIP3161F

Bulletin No.: PIP3161F
Date: May-2013
Subject:
Allison LCT1000 Clunk When Shifting Into Or Out Of Park Or On Start Up In Park
Models:
2003-2009 Chevrolet Kodiak C4500, C5500
2001-2007 Chevrolet Silverado Classic
2007-2013 Chevrolet Silverado
2001-2007 GMC Sierra Classic
2007-2013 GMC Sierra
2003-2009 GMC TopKick C4500, C5500
Equipped with a Allison LCT1000 Transmission
This PI was superseded to update model years. Please discard PIP3161E.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern
Customer may comment that trucks equipped with the Allison LCT1000 transmission may experience a clunk type noise on start up with the vehicle in park.
Customers may also experience a clunk noise when shifting into park from reverse or a drive range or when shifting from Park into Reverse.
The condition may be intermittent. Customers may also comment that when shifting into and out of park repeatedly without releasing the brake pedal, the clunk
into Park or into Reverse will become more frequent and repeatable.
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.
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