There are black plastic spacers that go between the leafs. Yours are probably missing.
<H1>Rear Leaf Spring Slap or Clunk Noise (Replace Spring Insert and Insulator) #03-03-09-002 - (12/02/2003)</H1>
</TABLE>Rear Leaf Spring Slap or Clunk Noise (Replace Spring Insert and Insulator)
1999-2004 Chevrolet Silverado 1500/2500 Series Pickups
2000-2004 Chevrolet Suburban 2500 Series
2002-2004 Chevrolet Avalanche 2500 Series
1999-2004 GMC Sierra 1500/2500 Series Pickups
2000-2004 GMC Yukon XL 2500 Series<A name=ss1-1409394><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1409394&pubid=297#ss1-1409394" target="_blank">
<H5>Condition</A></H5>
Some customers may comment on a rear leaf spring slap or clunk noise. This noise is most apparent when the vehicle is operated over irregular road surfaces.<A name=ss2-1409394><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1409394&pubid=297#ss2-1409394" target="_blank">
<H5>Correction</A></H5>
Verify that the rear leaf spring inserts (1) and insulators (2) are present on the leading and trailing ends of the overload spring. The insert may have broken apart from wear and fallen out. If the insert and insulator are not present, install new ones.
<H4>Important</H4>
On 1500 Series pickups, the vehicle must be raised to allow the springs to separate enough so the insert can be installed.
<A name=ss3-1409394><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1409394&pubid=297#ss3-1409394" target="_blank">
<H5>Parts Information</A></H5>
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<TR>
<TH vAlign=bottom align=middle>
Part Number</TH>
<TH vAlign=bottom align=middle>
Description</TH></TR>
<TR>
<TD vAlign=center align=middle>
15604067</TD>
<TD vAlign=center align=middle>
Insert, Spring Leaf</TD></TR>
<TR>
<TD vAlign=center align=middle>
15053476</TD>
<TD vAlign=center align=middle>
Insulator, Rear Spring Leaf</TD></TR></T></TABLE>
Parts are currently available from GMSPO.<A name=ss4-1409394><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1409394&pubid=297#ss4-1409394" target="_blank">
<H5>Warranty Information</A></H5>
For vehicles repaired under warranty, use:
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Labor Operation</TH>
<TH vAlign=bottom align=middle>
Description</TH>
<TH vAlign=bottom align=middle>
Labor Time</TH></TR>
<TR>
<TD vAlign=center align=middle>
E5168*</TD>
<TD vAlign=center align=middle>
Insulator and/or Insert, Rear Leaf Spring - One or All - Replace</TD>
<TD vAlign=center align=middle>
0.2 hr</TD></TR></T></TABLE>
* This is a new labor operation number. The next update of the Labor Time Guide will contain this new number.
<TABLE width="100%">
<T>
<TR>
<TD align=left width=778>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 whethe