Both automatic transmissions work flawlessly. The four-speed automatic is matched well to the engine's power and torque bands. The six-speed works better. Most of the time, we simply put it in Drive and drove. However, the six-speed features a simple manual-control mechanism that allows the driver to shift manually. When the manual mode is selected, it will not automatically upshift for you at redline but will go right up against the rev limiter, a strategy many enthusiasts prefer. An indicator light in the instrument panel helps remind you to shift.
The popular 3.5-liter V6 is quiet and smooth, producing 221 horsepower and 221 pound-feet of torque. GM has refined this overhead-valve engine, and even updated it with continuously variable valve timing. It's relatively smooth and quiet, with decent fuel economy: 17/26 mpg city/highway in the G6 GT.
The more powerful 3.6-liter engine that comes in the GXP is a modern, all-aluminum dual overhead-cam unit with four valves per cylinder. It also features variable-valve timing, and is rated at 252 hp and 251 pound-feet of torque, with fuel economy identical to the less-powerful 3.5.
Optional for the GT convertible only is a 3.9-liter V6. Like the 3.5, this is an older-style two-valve-per-cylinder pushrod unit updated with variable valve timing. It's rated only 222 horsepower, for all practical purposes the same as the 3.5; but with about 8 percent more torque (238 pound feet) it should deliver somewhat snappier acceleration.
We did a number of 90-0 mph ABS panic stops in a G6 GT on a deserted country road, and it stopped straight and true every time with no fade. The brakes have a nice, progressive power application through the pedal. Next Page