This bulletin applies to 2010-2012 Chevy Express and 2011-2012 Silverado 2500HD/3500 series trucks equipped with a 6.6L Duramax diesel engine. Some vehicles were involved in a mid-year change. Some may have been built with a flywheel housing that uses two different style seals (left side and right side seals are different).
If coolant is leaking out of the rear cover and these seals require replacement, note that the left side seal is an orange O-ring and the right side features a blue/green press-in-place seal.
The machining of the flywheel housing for each style seal is different and is not cross-compatible. If the flywheel housing is removed for service, replace the seals with the originally installed style on each side.
P/N …………….. SEAL
94056175.............Orange left side housing-to-engine seal
12644448.............Blue/green right side housing-to-engine seal