I am new to this group so please bear with me as I know this is an old thread. I have read a lot of the comments on this specific thread as I am trying to figure out what is my problem on my 2008 Yukon XL. Hopefully someone on here might be able to shed some light as I havent seen anyone post similar symptoms. When slowing down or letting off on accelerator, I start feeling a shudder. As someone mentioned, you shouldnt feel it when it goes into V4 mode but I feel it very well on this vehicle. It will do this around 20 to 35 mph. Once the vehicle slows almost to a stop, it goes back to V8 mode. Or, if just slowing down around those speeds, then accelerate, it goes back to V8 mode. Oil consumption is as most of you mention. I probably have to add 1qt every 3 to 4 weeks. When I purchased the vehicle used in 2012, it ran fine. It does not do it all the time though. Mileage is about 150000, give or take a few hundred miles. I also have a 2008 Silverado with the same engine and it runs fine. Almost perfect! Just trying to find a solution that will go easy in my wallet! Thanks in advance!