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Document ID# 1371224
2003 HUMMER
H2
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<H1>Info - Driveline Clunk #99-04-20-002B - (08/21/2003)</H1>Driveline Clunk
2004 and Prior Light Duty Truck Models</P>
2003-2004 HUMMER H2</P>
This bulletin is being revised to add model years. Please discard Corporate
Bulletin Number99-04-20-002A (Section 04 -- Driveline/Axle).</P>
<FONT color=brown>
<H4>Important</H4>
The condition described in this bulletin should not be confused with
Driveline Stop Clunk, described in Corporate Bulletin Number964101R
(Chevrolet92-265-7A, GMC Truck91-4A-77, Oldsmobile47-71-20A,
GM of Canada93-4A-100) or Bump/Clunk Upon Acceleration, described in
Corporate Bulletin Number99-04-21-004A.</P></FONT>
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Some owners of light duty trucks equipped with automatic transmissions may
comment that the vehicle exhibits a clunk noise when shifting between Park and
Drive, Park and Reverse, or Drive and Reverse. Similarly, owners of vehicles
equipped with automatic or manual transmissions may comment that the vehicle
exhibits a clunk noise while driving when the accelerator is quickly depressed
and then released.</P>
Whenever there are two or more gears interacting with one another, there must
be a certain amount of clearance between those gears in order for the gears to
operate properly. This clearance or freeplay (also known as lash) can translate
into a clunk noise whenever the gear is loaded and unloaded quickly, or whenever
the direction of rotation is reversed. The more gears you have in a system, the
more freeplay the total system will have.</P>
The clunk noise that owners sometimes hear may be the result of a buildup of
freeplay (lash) between the components in the driveline.</P>
For example, the potential for a driveline clunk would be greater in a
4-wheel drive or all-wheel drive vehicle than a 2-wheel drive vehicle. This is
because in addition to the freeplay from the rear axle gears, the universal
joints, and the transmission (common to both vehicles), the 4-wheel drive
transfer case gears (and their associated clearances) add additional freeplay to
the driveline.</P>
In service, dealers are discouraged from attempting to repair driveline clunk
conditions for the following reasons:</P>
<UL type=BULLET>
<LI>Comments of driveline clunk are almost never the result of one individual
component with excessive lash, but rather the result of the added affect of
freeplay (or lash) present in all of the driveline components. Because all of
the components in the driveline have a certain amount of lash by design,
changing driveline components may not result in a satisfactory lash reduction.
<LI>While some owners may find the clunk noise objectionable, this will not
adversely affect durability or performance. </LI>[/list]
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<TD align=left width=778><FONT size=1>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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<TD align=middle width=167><FONT size=2>WE SUPPORT VOLUNTARY TECHNICIAN
CERTIFICATION
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Document ID# 1371224
2003 HUMMER
H2
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