I was wondering if somebody knows this. I'm replacing the trans in my 2004 mustang gt. it's the 4r75 trans. I'm being told but the company that sold it to me that I need to update the ecm. What is that for, because I don't believe you can update these ecm like the newer cars am I right? I did read somewhere a while back that you don't actually update anything but you just clear the ecm and do the relearn with a better scanner type tool is that right or can someone tell me ?