Welcome to the Nation.

Looks like they are the same. Navigate over to gmpartsgiant.com and search for 08 Hummer and 08 Colorado. It will show the same crankshaft part number (12691185) for both. OEM is discontinued.

 

Thank you for the response!

To complicate the situation i just searched the casting number
#24100319 shows it's a crank for a 3.5L which means it's an 06 if i have my info correct.

This is from an 08 that i just brought back from Oklahoma (rust free)with bad engine. Bad engine was a used engine that was installed and knocked on startup.

 

I think the 3.5s had a different crank. The casting numbers could be the same though with a different grind for the 3.7.

 

I'll see what numbers i can get off the block tomorrow and try to identify what i have.

 

it appears the stroke is the same on 3.5 and 3.7 @ 102mm (4.02")
3.5 bore =3.66"
3.7 bore =3.76"