I've only had my V-6 G8 for a year. It's an 09 with less than 60xxx miles and during slow acceleration it hesitates to shift into overdrive until between 4k-5k RPM's. Another time it was revving up but going no where like the clutch was halfway depressed (even though it's an auto). The Shop says my torque converter is slipping. My question is; Is this a common problem? And do you really have to replace the whole transmission like they shop said, costing 4k?