not sure ur right on that my info off the ZR1 site says 4L60E was an option so I wonder if they would put a diferent ECM in the car IE is the spd ecm diff Then the 4L60E ecm also called my dealer here and the parts guy said that the parts book shows that option (4L60E) will do some more research url with ZR1 info Gene http://www.zr1.net/