Well here is the story I have a 2010 Chevy Suburban 2500 4X4 6.0L 6L90 Trans it has 6" lift 34" tires that are 33.50" stock gears were 3.73 and now has 4.56 gears. I changed the speedo and used the auto scale. The problem I am having is WOT from a dead stop takes off slow (feel like it is in 2nd) and then hits hard and chirps the tires. Then 2nd to 3rd the rpm jumps like the trans is slipping and shifts at 6k rpm. It seems to me that the rpm is hitting 6k before it gets to the shift speed. Driving normal it seems to shift fine. I purchased a HP VCM tuner to tune the trans to make my truck perform like a 6L90e should. I would like to supercharge this 6.0L but not until I can get the trans dialed in. I found out that this 6 speed tranny is very complex and difficult to tune.any help or direction would be great. Thanks