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<H1>Transmission Oil Leak, Abnormal Knocking Noise Heard at Idle (Diagnose and Repair as Requried) #03-07-30-037 - (09/04/2003)</H1></TABLE>Transmission Oil Leak, Abnormal Knocking Noise Heard at Idle (Diagnose and Repair as Required)

2001-2003 Chevrolet Silverado 2500/3500 Series Pickup Models

2001-2003 GMC Sierra 2500/3500 Series Pickup Models

with Duramax® Diesel (RPO LB7) and Allison® 1000 Series Automatic Transmission (RPO M74)<A name=ss1-1378771><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1378771&pubid=271#ss1-1378771" target="_blank">

Some customers may comment that an abnormal knock noise is heard when the engine is running, or that there is an oil leak from the bottom of the converter housing.<A name=ss2-1378771><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1378771&pubid=271#ss2-1378771" target="_blank">
<H5>Possible Cause</A></H5>

The Plate, A/transmission Flex (Flexplate adapter plate) to converter mounting bolts may have loosened from engine/road vibration. Use the diagnosis procedure given in this bulletin to diagnose the vehicle for this potential cause.<A name=ss3-1378771><A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1378771&pubid=271#ss3-1378771" target="_blank">
<H5>Technician Diagnosis procedure</A></H5>

If the under vehicle inspection reveals transmission oil leaking from the bottom of the converter housing to engine joint, perform the following diagnostic procedure.

For the diagnosis procedure, perform the steps indicated below.

  1. <LI =1>Disconnect both of the negative battery cables.
    <LI =1>Remove the transmission fluid level indicator.
    <LI =1>Raise the vehicle until the right front wheel and tire can be removed.

    <LI =1>Remove the right front wheel and tire.
    <LI =1>Remove the right front wheel house inner panel retainers (2).
    <LI =1>Disconnect any harness retainers attached to the inner panel.
    <LI =1>Remove the inner panel (2).

    <LI =1>Remove the positive battery cable nut and cable from the starter.
    <LI =1>Remove the solenoid nut and wire from the starter.

    <LI =1>Remove the starter motor bolts and reposition the starter.

    <LI =1>Remove the engine protection shield bolts and shield (skid plate).

    <A href="http://service.gm.com/servlets/RetrieveTif?pic=702519" target="_blank"><IMG alt="Click here for detailed picture of above image." src="http
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