The lazy burble is the first clue that this 32-valve V8 doesn't need to flex its muscles unless during extreme acceleration.
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| A fully-automatic 4-speed gearbox with overdrive brings all that Northstar power to the wheels, albeit without manual-mode actuation which is expected in this class. (Photo: Rob Rothwell, Canadian Auto Press) |
Rather it simply loafs about town, rarely breaking a sweat. When the time comes to speak its mind, the Northstar doesn't hold back. Power comes on smoothly and registers from sun up to sun down on the GXP's large tachometer. This isn't an engine that only delivers the "goods" in the final third of its rev band, but rather torque builds quickly at low rpms and remains in place until the twisting needle breaches 6,500 rpm. I was also impressed by the refinement of this Cadillac-derived power monger. Vibration and harshness never entered the picture, just honey smooth propulsion. Before delivery to the front wheels, all that propulsion needs to be harnessed by and fed through a capable transmission, which in the case of all 2004 Bonnevilles is a fully-automatic 4-speed gearbox with overdrive. As with the bulk of modern GM auto-boxes that I've tested, the GXP's version shifted flawlessly. Cogs were swapped crisply and shift points were always appropriate to ongoing needs and demands.
The aspect of the drivetrain that disappoints, depending of course on your drive-wheel preference, is its front-wheel drive
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| Torque steer in the front-wheel drive GXP is very well controlled, but unfortunately not completely eliminated. (Photo: Rob Rothwell, Canadian Auto Press) |
setup. The need to strap in a 275 horsepower V8 to safely launch the hefty sedan off-the-line by only its front wheels is no doubt the sort of complication that would have kept GM's engineering staff awake at night. The twisting force on the unequal length axles creates a natural tendency for the car to pull madly to one side or the other, which can easily be compounded by uneven road surfaces, uneven tire pressures and driver initiated steering inputs. In the case of the GXP, the engineers have done their homework and earned their pay. Torque steer is very well controlled, but unfortunately not completely eliminated. Under full acceleration the GXP's steering becomes hyper-twitchy, with a steady pair of hands needed to maintain a straight line or negotiate a curve.
