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).
| Years | Liters | Casting # | Trans | Flange Thickness |
|---|---|---|---|---|
| 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 |