Hello everyone I am doing my first ever engine and trans swap in my 08 RCSB. I have an LY6 6.0 from a 08 2500 silverado and a 4l80e trans from another truck.

Im trying to figure out if the wiring harness That I have with the 6.0 engine is going to work with the 4l80e trans? how can I tell? If not what r my options for getting a harness that will work or modifying the harness to work? Also wondering if i need to change the ECM?

Also someone told me that i would need to change the flywheel too. is this true? Any help will be greatly appreciated! I'm pretty new with this so if my questions don't make since feel free to ask or help clarify.