When you ponder unconventional cars, your mind might conjure images of a quirky Citroen 2CV traversing a field or a charming Innocenti 950 Spider winding through Alpine roads. It’s unlikely, however, that you’d immediately picture a full-size, front-wheel-drive American sedan with a distinctly rental-car-grade interior. Yet, exceptions exist to every rule, and the Pontiac Grand Prix GXP stands as a testament to automotive eccentricity. This W-Body platform, unexpectedly equipped with a potent V8 engine to challenge European sports sedans, was a reality you could once find on a Pontiac dealership lot. Hard to believe? Keep reading to delve into the wonderfully weird world of the Grand Prix GXP.
Throughout automotive history, vehicles featuring transversely mounted V8 engines driving the front wheels have been a rarity. Beyond a single generation of the Ford Taurus SHO and a smattering of Volvos, this configuration is most commonly associated with General Motors.
GM’s initial foray into this layout was driven by a desire for innovation with the Oldsmobile Toronado. They ingeniously paired a massive 425 cubic-inch V8 with a transaxle to deliver confident front-wheel-drive handling. However, despite its front-wheel-drive nature, the Toronado’s engine was still mounted longitudinally, incorporating a complex chain-drive system that was, to put it mildly, unconventional. As time progressed, GM’s motivation for front-wheel-drive V8s shifted from pioneering technology to more pragmatic considerations. American luxury car consumers desired the smooth, effortless power of a V8, and front-wheel-drive platforms with transverse engines offered advantages in weight distribution (improving fuel economy) and overall packaging compared to rear-wheel-drive setups. This rationale led to vehicles like the Cadillac Allante and Oldsmobile Aurora.
However, the automotive landscape began to change in the 2000s. The era of softly sprung, large sedans was waning, and a new demand for sharp, European-inspired handling and rear-wheel-drive vehicles emerged. While Chrysler was making waves with its rear-wheel-drive LX platform, GM, drawing on its heritage of transverse V8-powered cars, pondered: “How difficult could it be to adapt this concept to rival the best sports sedans from Germany?”
Instead of utilizing the familiar Northstar V8, GM undertook a significant re-engineering effort on its LS V8 engine family to enable transverse mounting. 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 integrated idler pulleys, the crankshaft was shortened, the starter was moved to the gearbox, and the engine block itself was a new casting. The complexity of this redesigned water pump manifold is truly remarkable.
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 L37 Northstar of 2004. While the horsepower gain was modest, the LS4 offered a more substantial increase of 30 lb.-ft. of torque, which was considered a worthwhile trade-off. The LS4 V8 also incorporated a technology familiar to Cadillac owners of the past: cylinder deactivation. The LS4 became the first LS-designated performance small-block V8 to feature this fuel-saving technology, even though GM was still grappling with its reliability issues, decades after Cadillac’s initial problematic attempts. The LS4, unfortunately, was prone to lifter wear problems, although these typically surfaced after other issues had already manifested.
Just as Porsche had its Tiptronic transmission, Pontiac developed its own paddle-shift system called Tap-shift. Intriguingly, both the left and right paddles functioned identically – push forward to upshift, pull back to downshift. However, in spirited driving, the effectiveness of Tap-shift was limited due to the exceptionally tall gearing. First gear stretched all the way to 56 mph, and second gear reached an astonishing 105 mph. In fact, if aerodynamic drag and tire limitations were removed, the Grand Prix GXP’s fourth gear, thanks to its 0.7:1 ratio, 2.92:1 final drive, and 255/45R18 front tires, could theoretically propel the car to 235 mph. This isn’t an exaggeration; these were the actual gear ratios and tire specifications.
Of course, all of this is contingent on the transmission functioning reliably. While GM possessed the robust 4T80-E transmission, the less stout MN7 4T65-E HD was chosen for the Grand Prix GXP. The issue was that the MN7’s torque capacity of 280 lb.-ft. was less than the LS4 V8’s output of 325 lb.-ft. This mismatch raised concerns about long-term durability. LS4 Store, a website dedicated to the LS4 engine, notes:
“The ‘HD’ designation signifies Heavy Duty. Otherwise, they are based on GM’s 4T65E transmissions, but with strengthened components. MN7s are factory-equipped with upgraded input and final drive sun gears, carrier assemblies, and enhanced drive sprocket thrust washers. Furthermore, MN7 cases are modified to accommodate relocated starter mounts.
4T65E-HD MN7s are factory-rated at 280 ft-lbs of torque on the engine side, and 400 ft-lbs of torque on the gearbox side. However, LS4s are factory-rated at 325 ft-lbs of torque at the crankshaft. Some speculate that this discrepancy may lead to long-term reliability issues for the stock transmissions. Regrettably, numerous cases of transmission failures have been reported. My own stock transmission—even with preventative upgrades—failed after 45,000 miles.”
Despite the transmission concerns, when functioning correctly, the Grand Prix GXP could accelerate from 0 to 60 mph in under six seconds. While not blistering by modern standards, this was undeniably quick for a mid-2000s sedan.
With power addressed, handling became the next challenge. A common issue with front-wheel-drive V8 cars is their inherent front-heavy weight distribution. The front end carries the engine, transmission, axles, and suspension components, while the rear primarily houses the muffler, fuel tank, and rear suspension. Pontiac’s engineers aimed to benchmark the BMW driving experience with the Grand Prix GXP, an ambitious goal akin to a fast-food chain aspiring to Michelin-star quality. Despite the inherent challenges, Pontiac engineers implemented an unusual solution to mitigate the handling imbalance.
The Grand Prix GXP featured wider eight-inch-wide 18-inch wheels with 245/45R18 tires at the front and narrower seven-inch-wide 18-inch wheels with 225/50R18 tires at the rear. Effectively, they reversed the typical staggered tire setup found on rear-wheel-drive performance cars like the Corvette. Staggered setups usually employ wider rear tires to promote safe understeer on rear-wheel-drive platforms. Pontiac’s “reverse stagger” had the opposite effect, counteracting some of the inherent understeer of the front-heavy platform.
The quirky details extended to the Grand Prix GXP’s interior. A large, soup can-sized knob positioned to the right of the gear lever appeared to control something significant. Perhaps suspension settings, drive modes, or traction control? In reality, it adjusted the brightness of the heads-up display, cycling through three levels. Changing the HUD information required using a small rocker switch atop the knob, offering limited display options. Page one showed all data, page two omitted the compass and temperature, and page three turned off the instrument cluster lighting for nighttime HUD-only driving. While the HUD wasn’t exclusive to the GXP, it was a feature absent from base Grand Prix models.
Unique to the 2005 Grand Prix GXP was a built-in G-meter in the driver information center atop the dashboard. This displayed peak acceleration, deceleration, and lateral G-forces, but only when the vehicle was stationary – a peculiar limitation likely imposed by legal concerns. To further emphasize its GXP identity, Pontiac equipped the car with sport seats featuring enhanced bolsters, a distinctive instrument cluster with a more legible font, turned aluminum trim accents, and the GXP emblem proudly displayed on the 160-mph speedometer.
Another noteworthy, though common to all eighth-generation Grand Prix models, design element was the dashboard. Pontiac, as GM’s “excitement” brand, decided the Grand Prix should have a driver-oriented center stack, a design seen in cars like the BMW E46 3-Series, Oldsmobile Aurora, and Honda S2000. While driver-focused, this often left the front passenger with less to interact with. The Honda S2000 and E46 3-Series offered minimal passenger amenities, while the Aurora integrated climate controls into the door panel. The Grand Prix, however, took a different approach, providing not one, not two, but four air vents exclusively for the front passenger. This seemed to amplify the well-known 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 oddly restricted G-meter is the fundamental ordinariness of the Grand Prix’s underpinnings. It remained a W-Body platform, ubiquitous on rental car lots and corporate fleets. The Grand Prix GXP is comparable to imagining Dodge inserting a V8 into a Stratus or Nissan dropping a V8 into an Altima.
The Pontiac Grand Prix GXP wasn’t the only recipient of the LS4 engine, but it was arguably the most unusual application. While the Impala SS was more prevalent, and the Buick Lacrosse Super was more understated, the delightful absurdity of the Grand Prix GXP deserves recognition. It’s akin to a slightly less refined Hellcat, a wonderfully excessive endeavor to push a platform beyond its intended capabilities. It’s doubtful Roger Smith envisioned this platform eventually housing more power than a 1987 Corvette, incorporating reverse-staggered tires, or featuring such extreme gear ratios. The Grand Prix GXP may not match the sophistication of an Infiniti M35 or Lexus GS430, but it undeniably possesses a far more captivating character.
Today, Grand Prix GXPs are available for purchase, generally priced between $5,000 and $8,000. In the current inflated car market, this represents considerable value, especially considering what you get. One example is currently listed for sale in California at a reasonable $5,900 with 138,000 miles. While current high fuel costs and the potential for mechanical issues might make a Grand Prix GXP a less than pragmatic purchase, it offers a unique and entertaining driving experience. Ultimately, shouldn’t cars offer a bit of fun?
And as a final note, for those who have reached the end, there’s an interesting tidbit. Positioned below the GXP in the Grand Prix lineup was the GTP, a supercharged 3800 V6 model that was arguably a more sensible option than the outlandish GXP. To promote the GTP, Pontiac enlisted Samuel L. Jackson, and an outtake from his voiceover recording session has circulated online. Be warned, it’s potentially unsuitable for workplace listening.
