I would like to know if a dealer can change the shift point in my 07 Yukon when in Tow-Haul mode? When in Tow-Haul mode driving 55mph it will not go into high gear, revs approx 2200rpm and when shifted out of Tow-Haul revs approx 1700 rpm. I have to drive over 60mph to get it to shift into high. A friend of mine just drove 3000 miles with his 08 Tahoe behind me, both of us pulling 3000lb identical trailers and both with the same engine and 3.73 gears and his stayed in hi gear at 1700 rpm in Tow-Haul mode all the time and mine would not.
If anybody else knows the answer, feel free to jump in!

 

I have a 2007 Tahoe and it shifts the same as your Yukon when towing. I push the tow/haul button (on) when I need a little more power and I push it again (off) when I am towing at flat freeway speeds. I am towing a 4500# trailer. I thought this was normal but maybe they have updated the ecm programming on the 2008 model. Next time your Yukon is at the dealer ask them if there are any updates avaliable. The next time I bring in my Tahoe I am going to ask.