Just bought 2012 gmc acadia with117k on it. Mint cobdition cosmetically and seemed to drive fine untill yesterday. It seems when im doing about 40 mph or 60 mph the rpms drop betweem 1700 and 2100 and i get the shudder/buck. If i let of gas or accelerate it powers through but when in steady speeds in traffic it gives those issues. Let me know what you think? Ive read several posts here that start with a lot of minor work and end withtorque converter. Hope this isnt the case.