6.6L LB7 , LLY with Manual Transmission 6sp ML6 Flywheel Housing Crack- kw diesel GMT560 vibration drive damage coolant leak rattle noise

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

03 04 C4500/5500 6.6L with 6sp ML6 Vibration or Coolant Leak from Cracked Flywheel Housing.

Some flywheel housing cracks on 6sp manual trans C4500/5500 trucks have been caused by vibrations created from driveline imbalances or excessive propshaft runout. These cracks typically occur around the flywheel housing to engine block mounting bolts. If the flywheel housing is cracked in certain places, a coolant leak may result. Propshaft modifications increase the chance of introducing an imbalance or excessive runout condition. Such propshafts are found on vehicles that have had the frames extended for custom applications. If a vehicle comes in for a vibration or coolant leak and a cracked flywheel housing is found, inspect for modified propshafts and correct any out of balance, excessive propshaft runout, or driveline angle issues per SI procedures in General Information - Vibration Diagnosis and Correction.

Note: The transmission yoke and the parking brake drum are balanced as an assembly but are not marked. This balance may have been disturbed on a previous repair or modification. During assembly, ensure that the alignment dowels between the flywheel housing and upper oil pan, as well as the alignment dowels between the flywheel housing and engine block, are in place. Because of the upper oil pan to flywheel housing dowels, the upper oil pan requires removal before the flywheel housing is removed. Assembly of an engine without these dowels will increase the potential for stress cracks on the flywheel housing.

.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.

(2003 -2004 Chevy MD C 4/5 Kodiak) and (2003-2004 GMC MD C 4/5 Topkick) equipped with the 6600 LB7 or LLY Engine and 6sp ML6 manual transmission

.