When discussing automotive oddities, images of quirky European compacts like the Citroen 2CV or the charming Innocenti 950 Spider might spring to mind. It’s less likely that a full-sized, front-wheel-drive American sedan, seemingly destined for rental fleets, would enter the conversation. Yet, the Pontiac Grand Prix GXP defies expectations and stands as a testament to automotive eccentricity. This W-Body platform, packing a potent V8 engine and engineered to challenge European sports sedans, was an improbable creation that Pontiac actually brought to life. Skeptical? Read on to discover the wonderfully weird world of the Pontiac Grand Prix V8 GXP.
Throughout automotive history, the configuration of a transverse V8 engine powering the front wheels has been a rarity. Beyond a single generation of the Ford Taurus SHO and a few select Volvos, this layout is most commonly found within the General Motors universe. GM initially explored this unconventional setup with the Oldsmobile Toronado, ingeniously pairing a massive 425 cubic-inch V8 with a transaxle to achieve confident front-wheel-drive handling. Interestingly, despite its front-wheel-drive nature, the Toronado still positioned its engine longitudinally, incorporating a chain-drive system in a truly unique design.
Over time, GM’s motivation for front-wheel-drive V8s evolved from showcasing flagship innovation to addressing practical market demands. American luxury car buyers desired the smooth, effortless power delivery of a V8, and transverse front-wheel-drive platforms offered advantages in weight management (contributing to fuel efficiency) and overall packaging compared to rear-wheel-drive configurations. This rationale led to vehicles like the Cadillac Allante and Oldsmobile Aurora.
However, the automotive landscape began to shift in the 2000s. The emphasis moved away from plush, softly sprung rides towards sharper, European-inspired handling dynamics, and rear-wheel-drive made a resurgence. While Chrysler was making waves with its rear-wheel-drive LX platform, GM, drawing on its history with transverse V8 engines, pondered a bold question: “How challenging could it be to adapt this concept to compete head-on with the leading sports sedans from Germany?”
Instead of utilizing the familiar Northstar engine, GM undertook a significant re-engineering effort of its LS V8 to accommodate transverse applications. While the cylinder head castings were indeed standard LS6 units, virtually everything else was redesigned. The water pump was relocated to a remote position on a manifold that cleverly integrated idler pulleys. The crankshaft was shortened, the starter was moved to mount on the gearbox, and the engine block itself was a fresh design. The complexity of this undertaking is perhaps best illustrated by the intricate water pump manifold.
The result of this extensive engineering was the LS4, a 5.3-liter V8 engine producing 303 horsepower – a mere three horsepower more than the 2004 L37 Northstar. While the top-end power gain might seem modest for such a significant redesign, the LS4 delivered a more substantial benefit: an extra 30 lb.-ft. of torque. The LS4 V8 also incorporated a feature familiar to Cadillac enthusiasts of a bygone era – cylinder deactivation. Notably, the LS4 was the first LS-designated performance small-block V8 to employ cylinder deactivation technology, despite GM still grappling with the refinement of this system, decades after Cadillac’s initial, less-than-successful attempts. The LS4 did encounter lifter wear issues, although these typically surfaced after other mechanical concerns had already manifested.
Just as Porsche had its Tiptronic transmission, Pontiac introduced its own paddle-shift system, dubbed Tap-shift. Intriguingly, both the left and right paddles functioned identically – push forward for upshifts, pull back for downshifts. However, the practical application of these paddles in spirited driving was somewhat limited due to the exceptionally long gearing. First gear stretched all the way to 56 mph, and second gear extended to an astonishing 105 mph. In fact, if traction and aerodynamic drag were somehow eliminated, the Grand Prix GXP’s fourth gear, thanks to its 0.7:1 ratio, 2.92:1 final drive, and 255/45R18 front tires, had a theoretical top speed of 235 mph. This is not an exaggeration; the gearing was truly that extreme.
Of course, these theoretical figures depend on the transmission holding up. While GM possessed the robust 4T80-E transmission, the MN7 4T65-E HD was chosen for the Grand Prix GXP. The problem lay in the MN7’s torque capacity rating of 280 lb.-ft., falling short of the LS4 V8’s 325 lb.-ft. output. This mismatch raised concerns about long-term reliability. LS4 Store, a website dedicated to GM’s LS4 engine, notes:
The “HD” stands for Heavy Duty. Otherwise, they’re based on GM’s 4T65E transmissions, but with some beefing up of various components. MN7s come from the factory with upgraded input and final drive sun gears, carrier assemblies, and upgraded drive sprocket thrust washers. Additionally, MN7 have modified cases for relocated starter mounts.
4T65E-HD MN7s are rated from the factory at 280 ft-lbs of torque on the engine side, 400 ft-lbs of torque on the gearbox side. However, LS4s come from the factory rated at 325 ft-lbs of torque at the crank. Some have speculated that this may lead to long-term sustainability issues for stock transmissions. Unfortunately, there are hundreds of cases of transmission demise. My stock transmission — even with life-prolonging upgrades — broke down after 45,000 miles.
Despite the transmission concerns, when functioning correctly, the Pontiac Grand Prix GXP could achieve a 0-60 mph sprint in under six seconds. While not blistering by today’s standards, this was genuinely quick performance for a mid-2000s sedan.
With power addressed, the question of handling arises. A common challenge with front-wheel-drive V8 cars is their inherent front-heaviness. The front end carries the weight of the engine, transmission, axle shafts, and suspension components, while the rear primarily houses the muffler, fuel tank, and rear suspension. Pontiac’s engineers aimed to benchmark the Grand Prix GXP against BMW, a comparison that might seem as ambitious as Taco Bell aspiring to Michelin star status. While both are enjoyable in their own right, they occupy different leagues. Nevertheless, Pontiac attempted a rather unorthodox approach to mitigate the handling imbalance.
The Grand Prix GXP was fitted with 18-inch wheels, eight inches wide, wrapped in 245/45R18 tires at the front. In contrast, the rear wheels were seven inches wide, also 18-inch diameter, but shod with narrower 225/50R18 tires. Effectively, Pontiac seemed to have reversed the typical Corvette tire setup. Staggered tire configurations usually involve wider rear tires and narrower front tires to promote predictable understeer in rear-wheel-drive vehicles. Pontiac’s “reverse stagger” aimed to counteract the inherent understeer of a front-heavy platform by somewhat mimicking oversteer characteristics.
The subtle eccentricities of the Grand Prix GXP continue within the interior. A large, soup can-sized knob is positioned just to the right of the gear lever. One might expect it to control suspension settings, drive modes, or traction control. However, this knob solely adjusts the brightness of the heads-up display, cycling through three levels. To alter the information displayed on the HUD, a small rocker switch atop the knob is used, offering limited customization. The display options are basic: page one shows everything, page two omits the compass and outside temperature, and page three disables the gauge cluster lighting at night for HUD-only operation. While the HUD wasn’t exclusive to the GXP, it was certainly not found on base Grand Prix models.
Unique to the 2005 Grand Prix GXP was a G-meter integrated into the driver information center atop the dashboard. This G-meter displayed peak acceleration, deceleration, and lateral g-forces, but only when the vehicle was stationary – a restriction likely imposed by cautious legal advisors. To further distinguish the GXP, Pontiac equipped it with more aggressively bolstered sport seats, a unique instrument cluster featuring a more legible font, turned aluminum accents, and a GXP emblem proudly displayed on the 160 mph speedometer.
Another noteworthy, albeit shared with all eighth-generation Grand Prix models, design element was the dashboard. Pontiac, as GM’s “excitement” brand, opted for a driver-centric center stack in the Grand Prix. This design, common in cars like the BMW E46 3-Series, Oldsmobile Aurora, and Honda S2000, prioritizes the driver’s ergonomics but can leave the front passenger feeling somewhat neglected. While the Honda S2000 and E46 3-Series offered minimal passenger-side controls, the Aurora innovatively integrated climate controls into the door panel. The Grand Prix, however, took a different approach, providing not one, not two, but a staggering four air vents exclusively for the front passenger. This design seemed to amplify the long-standing joke about GM designing air conditioning systems first and then building cars around them.
What truly amplifies the peculiarity of the special V8, reverse-staggered tires, and the lawyer-restricted G-meter is the underlying ordinariness of the Grand Prix. It remained a W-Body platform vehicle, a common sight in rental car lots and corporate fleets. The Grand Prix GXP is akin to Dodge installing a V8 in a Stratus or Nissan dropping a V8 into an Altima – unexpected and slightly absurd.
The Pontiac Grand Prix GXP was not the sole recipient of the LS4 engine, but it was arguably the most unconventional application. While the Chevrolet Impala SS was more prevalent and the Buick LaCrosse Super offered a more understated performance profile, the glorious absurdity of the Grand Prix GXP is something to be celebrated. It’s a somewhat less refined, yet equally excessive, take on the muscle car formula, pushing a platform far beyond its intended capabilities. It’s unlikely that Roger Smith, former CEO of GM, envisioned this platform eventually boasting more power than the 1987 Corvette, incorporating reverse-staggered tires, or featuring such remarkably tall gearing. The Grand Prix GXP may not match the overall sophistication of an Infiniti M35 or a Lexus GS430, but it is undeniably more intriguing than either.
Today, Pontiac Grand Prix GXPs can be found for sale, generally priced between $5,000 and $8,000. In the current inflated car market, this represents considerable value, especially considering the unique package offered. One example is currently listed in California for a reasonable $5,900 with 138,000 miles on the odometer. While high fuel costs and potential mechanical uncertainties might make a Grand Prix GXP a less than pragmatic purchase, its sheer entertainment value is undeniable. After all, shouldn’t cars inject a bit of fun into our lives?
And as a bonus for reaching the end, consider the Grand Prix GTP, positioned below the GXP in the lineup. Powered by a supercharged 3800 V6, the GTP was arguably the more sensible performance variant. Pontiac famously enlisted Samuel L. Jackson to promote the GTP, and an amusing outtake from his voiceover session has circulated online – perhaps best not played aloud in a professional setting.
