Just bought a 2012 GMC Acadia with117k on it. Mint condition cosmetically and seemed to drive fine until yesterday. It seems when I'm doing about 40 mph or 60 mph the RPMs drop between 1700 and 2100 and I get the shudder/buck. If I let off the gas or accelerate it powers through but when at steady speeds in traffic it gives those issues. Let me know what you think. I've read several posts here that start with a lot of minor work and end with torque converter. Hope this isn't the case.