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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1677 (Engine Mechanical - 6.6L (LMM) - Repair Instructions - Off Vehicle (2 Of 3)) >> Crankshaft and Bearing Cleaning and Inspection >> Crankshaft Bearing Selection Grade Chart Method

Crankshaft Bearing Selection Grade Chart Method

WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
Stamp ID Main Journal Conn. Rod Journal
No Stamp STD STD
M20 R20 0.020 in 0.020 in
    Fig 1: Inspecting Crankshaft For Stamping Indicating Undersized Main And/Or Rod Journals
    GM1775612Courtesy of GENERAL MOTORS CORP.
    NOTE: All crankshafts that have been machined have a steel stamping (1) on the 1st counterweight.
  1. Inspect the crankshaft for stamping (1) indicating undersized main and/or rod journals.
    2. Fig 2: Locating Engine Block Main Bearing Bore Grade
    GM2363959Courtesy of GENERAL MOTORS CORP.
  2. The engine block main bearing bore grade is indicated on the top of the high pressure pump bore. The first 5 digits (1) of the top number, next to the 2D bar code, indicate the main bearing bore grades for main bores 1-5, respectively. In the case of the illustrated example, block number 1222292430009 has main bearing bore grades of:
    • Main bearing bore #1 = Grade 1
    • Main bearing bore #2 = Grade 2
    • Main bearing bore #3 = Grade 2
    • Main bearing bore #4 = Grade 2
    • Main bearing bore #5 = Grade 2
    3. Fig 3: Identifying Crankshaft Main Bearing Journal Grade
    GM2363961Courtesy of GENERAL MOTORS CORP.
  3. The crankshaft main bearing journal grade is indicated on the back side of the rear counterweight. The first 5 digits (1) equal the grade for crankshaft main bearing journals 1-5, respectively. In the case of the illustrated example, crankshaft number 221112550900 has main journal grades of:
    • Main journal #1 = Grade 2
    • Main journal #2 = Grade 2
    • Main journal #3 = Grade 1
    • Main journal #4 = Grade 1
    • Main journal #5 = Grade 1
  4. Match the cylinder block grade and the crankshaft journal grade, refer to Crankshaft Bearing Selection Specifications .
  5. From the Crankshaft Bearing Grade chart, determine which bearing grade (color code) is required.
  6. Verify the crankshaft bearing clearance using the plastic gauge method.
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