2015 express 5.7 8speed trany 2 wheels drive. So after putting on the lift 7inch max tracks also 20x12.5 toyo tires. When I'm on the highway if it's flat it's ok othe then that it's shifting back in forth from 8 to 7th gear. So do I need a different gear set up? Would a tunner take care of the problem?
Buckeye, I had the same issue. I am running 4 inch lift, bilsteins at 2.1, and 35s. Your higher and wider so I am sure you are having issues.
Only way to recalibrate on a 2015-2016 is too get a diablo tuner. But with this you will need a DCX PCM or send your pcm in ($1200 new). I was lucking to have bought mine used for $650.
I just got a hemifever 91 oct tune and its amazing. averaging 17.1 mpg and acceleration and shifting is much improved.