Two Pontiac GTOs for One Mercedes-Benz CLK55 AMG - Transmission - Sport Coupe Comparison

Besides the fact that our GTO test unit had less than 1000 miles on it when we ran our numbers, another element of the pair's performance differential comes down to transmissions. The Mercedes trans is a computer- controlled five-speed automatic. It offers Sport, Comfort (Winter), and Manual modes. Gear and rearend ratios are perfectly matched to the engine's power curve and keep it on boil all the time. It breathes the throttle just a hair on full-commando shifts to avoid shocking the driveline and shifts seamlessly on part-throttle gear changes. It's also equipped with Mercedes's excellent TouchShift function: Pop the shifter to the right for upshifts, tug it left for downshifts. Select the Manual mode, and manumatic shifting control is handed over to the steering-wheel-mounted paddle switches. All said, it's one of today's best and most versatile automatics.

The Pontiac's transmission also boasts three modes: forward, backward, and stop. It's a strictly conventional four-speed unit that behaves well enough. It has none of the manumatic controls you'll find in the Benz, and the ratios are wider than on today's best five- and six-speed units. In spite of the GTO's abundant torque curve, the power fall-off at each shift is far greater than that of the Mercedes, especially on the 3-4 change.

It isn't that this transmission is so awful; it just saps a lot of driver involvement out of the experience. The car's patron saint, GM vice chairman Bob Lutz, acknowledges: "We would've loved a more sophisticated trans, but we didn't have anything certified to go with this engine. To start from scratch with a five- or six-speed, for this relatively small sales volume, would've taken too long and cost too much." Fortunately, Pontiac offers a superb alternative that you can't get on the CLK55 at any price: a proper--and outstanding--six-speed manual. We've acknowledged the GTO's cornering prowess in previous tests. Even though the Mercedes lays down slightly better numbers, it takes nothing away from the Pontiac's solid, predictable, enjoyable chassis manners. Senior road-test editor Chris Walton comments: "I was busier trying to keep the rear end planted in this car than in the manual-transmission version, but it'll still drift its way through the slalom happily."

The Mercedes is more neutral, says Walton, and "it feels like this car has been through a slalom or two before." Indeed, it threaded through our 600-foot conefield at an average speed of 66.4 mph versus the GTO's 62.5-mph run. Interesting is that both put down nearly identical skidpad performances, the Mercedes's 0.82g rating just nipping the Pontiac's 0.81. This indicates that, while their ultimate grip performance is the same, the Mercedes manages those left-right-left transitions better.