Portsmouth Chevrolet claims the torque converter was failing and needed replacement to resolve the shuddering during transmission shifts between gears (6L80 automatic transmission). After replacing the torque converter the transmission technician failed to resolve the shuddering when shifting between gears. The shuddering occurs during transition between AFM V8 and V4 modes (Active Fuel Management). The suddering also occurs when in V8 (all eight cylinders active) while under load, traveling up a grade and accelerating, while the transmission is in 6th or 5th gear. The load or grade under acceleration would typically cause the transmission to downshift from 6th or 5th into the next lower gear. After the torque converter replacement the vehicle continues to shudder under conditions in full V8 mode and also noticeable when dropping into V4 mode with the AFM and while the vehicle is in 6th or 5th gear.

Portsmouth Chevrolet has a technician who refers to himself as a "world class technician" who works on all the new Corvettes, but this technician cannot fix this issue or chooses not to fix the shuddering after replacing the torque converter for "shuddering." Makes one wonder if the torque converter was the problem in the first place.

The vehicle had 46,000 miles when the symptoms started to occur and now at 50,000 with a new torque converter the vehicle is no better than when the issue started at 46,000. I opened a case with GM Support and the dealership has given up on solving the problem; telling GM Support the vehicle was fixed. GM has a serious problem with the TCM (transmission control module) management of the transmission shifting, without the reduced cylinder activation (AFM V4), but the issues occur in both AFM modes and the shuddering is unaccepatable.