Originally Posted By: Adrian
These 6spds don't seem to work as well with a gas engine from my limited experience with the Yukon(vs my 6spd/Duramax). It never seemed to be in the right gear wherever I was driving, as if you needed to kick it down to a lower gear to wake the engine up. I guess they're trying to squeeze all the mileage they can out of it, and the tranny is set-up as such. All in all, I don't think it was anymore economical than my diesel and imo, not worth 61K(maybe 40-45K).


I know exactly what you are talking about. My 08 Sierra Denali has the 6.2 and six speed. I had mine for about two months before I had it tuned. Woke it up big time, my mileage went up 15% and the thing shifts wonderfully now. The down side to this is GM knows if the thing has a tune and the warranty is effectively voided. You can program a spare ECM, swap it out as needed, but the tranny has its own control module inside the tranny, so you can't swap it out very easily. It can only be tuned via on board lap top and interface cables. There is a guy who sells a kit now, where I bought mine from. He sends you a control unit that you just plug into the interface adapter, then you down load the tune for the engine and tranny. You drive the rig, copy the monitoring file to a disk and email it back to him. He looks the data over, tweaks the tune as needed, then sends the file back to you. They you just down load the updated file. He also includes five other tuning profiles based on the data you send him and all you do is select the tune you want to run (towing, racing, economy, etc). My truck does not drive anything like it did stock. Pretty slick. I don't like to advertise, so if anyone is interested, PM me and I'll give you his name and web sight.