The V8 that comes on the SS delivers 303 horsepower and 323 pound-feet. That's more power and torque than any other entry in the class, but the chassis that comes with it needs taming. The traction control system simply gets behind in its orders whenever you slam the throttle open at a stop in first gear, and lets the left front tire spin wildly for a few seconds until it finally catches up. While we appreciated the extra power and torque available in a kickdown or passing situation, and we loved the brawny, muscular sound of this engine at full throttle, it's a challenge to launch cleanly and quickly at the same time. Besides wheelspin, there's a lot of torque steer. Slam down the throttle and you'll feel a significant tug on the steering wheel. The V8 also features Active Fuel Management (formerly called Displacement on Demand), which shifts between eight-cylinder and four-cylinder operation, depending on speed and load. The V8 was EPA-rated at 18/28 city/highway for 2006 and shouldn't be any different for 2007.

All Impalas come with a MacPherson-strut, coil-over-spring independent front suspension, with gas-charged struts and a stabilizer bar. The rear suspension uses a trailing tri-link setup with gas-charged struts and coil springs. A rear stabilizer bar is standard on all models. Suspension tuning is matched to each engine. With all three, however, there is a lot of pitch, dive, and roll in the chassis, plus a lot of uncertain driving moments with the added power of the SS. The SS, particularly, drives as though its chassis needed more development time before production. Steering on all models is over-assisted, fairly numb and uncommunicative.

The Impala's four-wheel disc brake system (vented in front, solid in rear) represents an improvement over previous generations. Comprising new front brakes, improved rear brakes, and a new brake booster, the system is designed for quieter operation, longer pad life, and more resistance to brake pulsation. The new ABS includes Electronic Brake-force Distribution. On the road we found the Impala's brakes very much to our liking: powerful, direct, and linear, with a nice, progressive ratio of pedal travel to stopping progression.

The new Generation 7.0 OnStar offers Turn-by-Turn navigation with the optional Directions and Connections service. Turn-by-Turn navigation directs the driver through the route by using the digital readout lines in the radio head. Directions are downloaded by the OnStar advisor to the vehicle and can be played back or paused anywhere from start to destination. Besides being easy to use (all directions are downloaded to the car by an advisor) Turn-by-Turn offers an affordable system that is always up to date (no need to purchase map updates).

Summary

The Chevrolet Impala LT and LTZ models are pleasing to drive, whether equipped with the 3.5-liter or 3.9-liter V6 engines. The SS cuts a conservative but dashing figure, with its quiet badging and giant five-spoke, 18-inch wheels; but it has more power than it knows what to do with, though we did enjoy its loud, authoritative exhaust rumble). Overall, the Impalas are good cars, though they don't match the sophistication of some of the competition.

NewCarTestDrive.com correspondent Jim McCraw filed this report from Dearborn, Michigan

Model Line Overview

Model lineup:Chevrolet Impala LS ($20,830); LT ($21,440), LT with 3.9-liter ($24,160); LTZ ($26,250); SS ($27,855)

Engines:211-hp 3.5-liter ohv V6; 233-hp 3.9-liter ohv V6; 303-hp 5.3-liter ohv V8

Transmissions:4-speed automatic

Safety equipment (standard):frontal airbags, side-impact airbags, side-curtain airbags

Safety equipment (optional):ABS, EBD; traction control; tire-pressure monitor

Basic warranty:3 years/36,000 miles

Assembled in:Oshawa, Ontario, Canada