Originally Posted by TransEngineer
Yes, the 66RFE does shift through all 6 gears in normal driving.
Swapping in a 66RFE (in a 2010-2011 truck) would require new PCM software to enable the correct shift pattern. And that creates a concern for keeping the software and hardware matched. Suppose you installed a 66RFE (with new PCM software). A year later, you go to your dealer for an oil change, and he "helpfully" updates your PCM to the latest level of software (for a 545RFE truck!!). So there are some issues with doing this.... but I'll see if any of my colleagues think it might be a possibility.
If your dealer installs the transmission it goes in your service file and will be added to your vehicle serial#... so I was told by my dealer back in 2011. In my case with an 09 it would void my lifetime warranty but who cares. The problem is the tcm is in the pcm...it is not a stand alone control like the 68RFE. So we have to figure a way to swap our pcm to a 2012 HD 2500 Hemi of the same model. The 545RFE/65RFE has a hp sucking gear ratio, it's garbage. The 66RFE are spread even and better appart and it's much stronger. Hell yeah I'd go for one in a heart beat! I've never checked but we need to find out if the harness is simular between either of the three. Possibly we may be able to use the 65RFE harness....just a thought....or hopefully even the 545. Then all we have to do is tune it respectively to accept the shift schedule (that would be on a wing and a prayer). Or worse case senerial swap out the pcm to the correct one.