C 3500 Truck 2WD V8-6.6L DSL Turbo VIN 1 (2002)
Crankshaft Main Bearing: Technical Service Bulletins
Diesel Engine - Main Bearing Cap Bolt Identification
Bulletin No.: 06-06-03-003
Date: January 20, 2006
INFORMATION
Subject:
Information On Longer Main Bearing Cap Bolts Required For Certain 2001-2006 LB7, LLY, LBZ Duramax(TM) Diesel Engines
Models:
2001-2004 Chevrolet Silverado
2003-2004 Chevrolet Kodiak C4500/C5500 Series Models
2006 Chevrolet Express Vans
2001-2004 GMC Sierra
2003-2004 GMC TopKick C4500/C5500 Series Models
2006 GMC Savana Vans
with 6.6L Duramax(TM) Diesel Engine (VINs 1, 2, D - RPOs LB7, LLY, LBZ)
Main Bearing Bolt Length Identification
This bulletin is being published to aid technicians in how to identify the Mid-Year change to the Main Bearing Bolt Lengths. During the early production
of 2006 Duramax(TM) diesel engines, a design change was made to the bearing cap bolt and bore for increased robustness. This change includes a 4 mm
(0.15 in) longer main bearing cap bolt along with a deeper tapped hole and a deeper counter bore. The new bolt can be identified by a raised circle
formed into the bolt head as shown in the above illustration.
Note:
Use of the incorrect bolt will result in engine damage. The shorter bolt will not have enough thread engagement in the newer blocks due to the deeper
counter bore, and the longer bolts will bottom out in the older blocks before achieving the proper clamp load. Measurement of the bolt length is not a
reliable method of identifying the bolt, as the bolts will stretch to a varying degree after installation. The main bearing cap bolts should not be reused
in service.
When performing service work on ANY model year Duramax(TM) engine, the main bearing cap bolts must be replaced with the same type of bolt that
was originally installed. Use the raised circle identifying mark on the bolt head to determine which bolt to use.
It is possible that a prior year vehicle (2001+) could have the newer block with a deeper counter bore if it had an engine replacement after the block
change was implemented in production. This is possible because some long block service engines may be built with new production components, such as
engine blocks.
In the event that the raised circle identifying mark on the bolt head cannot be relied upon to determine the correct bolt usage, the engine block production
date/time stamp may be used.
