So I have had this truck 1 yr now and recently the tranny feels like it is staring to hit gears harder. Especially when slowing to a red light but then accelerating as it turns green, it down shifts then feels like it gets confused and finally hits up a gear. I have 69K miles and figure the tranny fluid and filter needs changing. Any thoughts?
AWD Transmission acting strange on 2007 GMC Sierra Denali
Sounds like a transmission problem, cheapest thing to try is to change the transmission oil drop the transmission pan and inspect for debris and change the filter.
It soundsnlike you are dealing with a bad transfer case. I would start there. Either way you are looking at a 1000+ in repairs. I just replaced the transfer case in my 2003 sierra 1500 Denali, myself.