The AERA Technical Committee offers the following information on crankshaft replacement caution for 1998-2003 GM 4.3, 4.8, 5.3, 5.7 and 6.0L engines. Design changes in the flywheel flange thickness have been made to some crankshafts used in the above-mentioned engines. This bulletin is being re-published with additional information.
The later crankshafts are shorter on the flywheel flange as seen in the listing below. These changes are due to the many different vehicle / transmission combinations being built by GM.
A flywheel spacer ring (GM Part #125635320) and a longer bolt set (GM Part #12563533) is required when using a thin flange crankshaft to replace a thick flange crankshaft.
If the crankshaft is being used in a standard shift application you also need pilot bushing (GM Part #12557583 or 12479894).
|98 early||4.3L||236, 255||V-6||1.62 thick flange|
|98+up||4.3L||236, 255||V-6||1.500 thick flange|
|99-00||4.8L||312||V-8 M/T||1.250 thick flange|
|99-00||6.0L||215||V-8||1.250 thick flange|
|99-05||4.8L||482||V-8 A/T||.857 thick flange|
|01-05||4.8L||482||V-8 M/T||.857 thick flange|
|99-05||5.3L||216||V-8 A/T||.857 thick flange|
|97-05||5.7L||216||V-8||.857 thick flange|
|01-05||6.0L||216||V-8||.857 thick flange|