6L50 6-Speed Auto Transmission (RWD) Interchangeability
 

Is a 2011 STS 6L50 transmission completely compatible with a 2008 STS 6L50 transmission?

My vehicle is a:
2008 Cadillac STS 3.6 V6 Platinum RWD

From what I can tell: Yes it will go across. Major revisions seem to be 2007-and-earlier got revised for 2008-and-later. I'd suggest getting the TCM with it to be safe.

I don't know of anyone doing this anywhere so take this advice at your own risk. Maybe consult your local ATRA-certified transmission shop for good measure.

Let us know how it goes.