If you do manage to get an unlocked tune, I have been slowly adding the 6th gear tables with CAX files. I use these with both the Duramax Tuner tune and a PCMP tune.
Grab the CAX file here:
https://piglab.reaperlegion.net/aut...ob/master/Calibrations/DF6.cax?ref_type=heads
I need to upload some changes from my tuning laptop, I seem to recall finding a couple more tables since that initial upload. Just check that link periodically for the latest version.
Edit: no new tables (yet...), but I did find this in my notes:
EFILive 6-speed shift pattern labels are wrong! Actual mapping:
* Pattern A = Normal
* Pattern B = Tow/Haul
* Pattern C = 4WD Lo
* Pattern D = Trans Hot
* Pattern E = Normal (selector in 2)
* Pattern F = Trans Hot (selector in 2)
* Pattern G = Tow/Haul (selector in 2)
* Pattern H = 4WD Lo (selector in 2)