Circuit or method to tell 6l80 you are in a different ratio in tranfer case?

[whypave]

in a non GM vehicle with a two speed transfer case (2:1 and 1:1) has anyone found a way to tell the 6l80 that it is in low range so that it modifies the VSS signal and still has the correct MPH info for shift points? I am running a 2008 corvette OS from tunefiledepot.com to allow for tap-shifting so it doesn't really "know" about a transfer case. But then again I looked at the 2011 Silverado tune file and it has different A and B shift patterns and it looks like the B shift pattern may be for low range based on the must lower shift speeds in the table but I see nothing to indicate how the trans knows to be in which pattern. I would have thought in the trucks with a two speed transfer case the gear ratio would change dynamically and update the VSS calc. but i don't see any evidence of being able to set a transfer case ratio in Say the speedo calculator screen.

So is there a way to wire up a switch to tell the transmission what shift pattern to use and what the "final drive ratio" is or is a BCM required?

Thanks for any assistance!

[slow67]

It looks like you add pins to the PCM tune, not the TCM (set the transfer case ratio in H0121, and the speed limiter in H0155).