2006 Pontiac GTO Project Car Suspension Bushings & Torque Converter - Project Head Poncho - Tech

Our Newest Street/Strip Project Car Takes Command Of GM High-Tech's Offices

Vinnie The Hitman Aug 1, 2008 0 Comment(s)

The 2004-2006 Pontiac GTO has been the focus of much scrutiny over the past few years. Traditionalists considered the car "unpure" and accused it of not living up to the legendary GTO name. Meanwhile, modern armchair auto "experts" quickly dismissed the car as a plain-looking, uninspiring performance coupe. Well, it's time that these cars received some well-deserved praise, so we at GMHTP will now stand up and defend the neo-GTO. This may offend some of you die-hard Tin Indian fans, but let's face it-this is the best Pontiac that Pontiac never built.

With the GTO's rip-snorting LS1 (and later, LS2) powerplant, fully capable four-wheel independent suspension, and lavish leather-lined interior, we can't think of any other GM-branded car of late that is as nicely polished as the down-under Holden Monaro from which the GTO is based. One look underneath and it's apparent that Holden (aka GM of Australia) went with a European approach for precision engineering, resulting in a car that handles and stops as well as it goes.

But as good as this car was, Pontiac had a tough time selling them. On paper, it seemed like a great idea, but the PMD boys were looking sales disappointments in the face, as only 30,000 units were sold during the GTO's short three-year lifespan. Luckily for us GM fans, these low quantities make the GTO a rather uncommon find today, and they are the best-kept secret since the '64 model. So what if it looks like a '90s Jellybean? It'll trounce just about anything in the lane next to it-and, in our opinion, look handsome doing it.

GT OwnershipThe best way to experience a GTO is to own one, so we found one we wanted from an original owner in arrest-me Torrid Red with just 21,000 miles on the clock. Equipped with a sumptuous black leather interior and the desirable 4L65E automatic transmission, our LS2-powered Holden, er, Pontiac, made itself at home in our garage. Considering that no other GM car can give you such bang for the LS2 buck, it's a logical and cost-effective choice until the new Camaros go on sale.

The first order of business was to improve the GTO's appearance with subtle and noticeable aesthetic enhancements. For the front, we found a factory Torrid Red Sport Appearance Package (SAP) front spoiler. Pontiac dealers no longer stock these parts and the market has adjusted accordingly, so it cost us an arm and a leg. As a matter of fact, we paid $630 for it, which is nearly double of what it was when new. To match the front spoiler, we also popped in a set of funky-fresh SAP front grilles, which drained our wallets yet another $500. As expected, these discontinued OEM parts will remain pricey, even as cheaper aftermarket copies are being introduced to market. Remember, you get what you pay for.

In back, we took a good look and considered the rear end a bit too thickset. The rear decklid spoiler has a lot to do with that bulky look, so we quickly removed it and installed a lower profile fiberglass decklid spoiler from Vengeance that is much lower in profile and uses the existing mounting holes in the trunklid for a quick and easy installation. The only thing we had to do was fork over $150 to have it painted. With the wing's cost included, it was a $500 project that greatly changed the look of our Goat. It also improved rearward visibility from behind the driver seat. Lastly, we sourced a set of Australian-market VT Coupe taillamp assemblies and within 30 minutes, greatly transformed the way our car looked from behind. They sure look great, but make note that they are not DOT legal as they lack the requisite rear and side reflectors. In the end, the car looked real tough and in charge, so we came up with the name "Head Poncho."

With some blingage (yes, we just made that up) added to our ride, it was time to see how effectively the LS2's 400 hp was making it to the ground. The car had some slight mods already performed by the original owner, but they were so minor that we still considered the car stock. With our Head Poncho pointed towards Old Bridge Township's Raceway Park near Englishtown, New Jersey, we readied ourselves for a baseline run. With a quick burnout to clean the tires, we staged the car at about 1,200 rpm on the converter-and with the factory 18-inch tires inflated to 20 pounds in back, we were able to achieve a rather impressive 12.97 at 108 mph on a chilly 50-degree night. For the modifications it has (160-degree thermostat, eliminated resonator, torque management removed) it is right on par with what an A4 GTO should run. Happy with our times, we then looked to harness the power that we already had and put it down to the ground with some subtle driveline modifications.

GT Operations
To effectively increase chassis efficiency, we knew that our Head Poncho needed only a few parts to optimize hook on the starting line. By eliminating some play in the suspension in key areas of the multi-link rear suspension, gains in weight transfer and optimized squat would help us in the long run. Rear wheel "squat" on the GTO is both good and bad. It's good because it preloads the rear on an automatic car and instantly gives you weight transfer before the car is even moving.

However, with increased suspension compression comes a loss in rear camber and a gain in toe (this is bad). Excessive camber and toe prevents the tire from having a flat and even footprint on the road surface, which can actually limit traction. To resolve this, you need to let the car squat just enough to get most of the 3,800-pound GTO's weight onto the rear tires, but not so far as to let it compress to the point where you alter the contact patch and lose traction.

The cheapest and most effective way to control this squat and its nasty cousin, wheelhop, is to install airlift springs, which are also known as "Drag Bags" in GTO parlance. They go inside of the rear coil springs and, with an hour or two of labor, will limit the amount of total suspension compression when stalling up the converter. This also helps improve the ride quality as the stock rear springs are a bit on the soft side. To help control wheelhop, or more accurately, axle tramp, installing polyurethane suspension bushings is also key. This eliminates movement between the points of attachment for the control arms and the rear cradle that everything is connected to. Manual-trans owners will benefit from a bushings upgrade more than an automatic owner will, but, in our opinion, no GTO is complete without a set. To help us with these essential items, we gave the experts at BMR Fabrication of Thonotosassa, FL, a call.

BMR offers many parts to help GTO owners with their wheelhop and traction issues. We started our shopping list with its Drag Bags, polyurethane outer rear control arm bushings with adjustable toe, polyurethane cradle bushings for the two front attachment points, and a polyurethane rear insert for the factory rear differential support. Together, these low-buck mods transform the GTO's tendency to be a bit elusive in feel into the taut, yet very compliant, GT coupe that it was born to be. Even better, traction is improved.

Conversion Factor
The next part of the driveline equation was an update of the factory torque converter. Although it's great for those who want slower e.t.'s and reduced throttle response, the heavy and uninspiring factory 12-inch torque converter does nothing else right. To remedy this, we looked to Precision Industries for one of its 9.5-inch Vigilante performance torque converters. Although there are many other converters in the marketplace, you definitely get what you pay for. With a rollerized internal design with fully brazed fins and a billet steel front housing, we are very confident in its robust construction and know our money will go a long way.

While we could have chosen its stout three- or even stronger five-plate lockup clutch design, we didn't think it was necessary at our power level so we went with a conventional single-plate lockup clutch. For those with more modified GTOs, it makes more sense to go with a multiple-plate setup, as it will allow you to engage lockup at wide open throttle when your vehicle has been modified to do so.

As for stall speeds, everything is relative. Many get greedy and get a very high stall converter, but the fact of the matter is, you need to take the vehicle's weight, gearing, and horsepower into consideration. Too much stall just wastes fuel and hurts e.t. Since we already knew that aftermarket converters tend to stall a bit higher than advertised in a GTO (due to the vehicle's increased weight and 3.46 gearing) we went with a 3,200-rpm stall rating for our Head Poncho, expecting to see 3,400 rpm. It was a smart starting point for our relatively stock LS2 and the GTO platform.

To help install our BMR suspension bits and Vigilante torque converter, we looked to Jack Meng of JM Motor in Queens, NY. Jack is well known in the LS community for offering quick turnaround and quality work so we knew we would be in capable hands. Within a day, he was able to get our car back on the ground and ready for the track.

Because tire section widths are quickly limited to 245 in the back of a GTO, you'll have to massage the rear quarter panels in order to fit anything wider. Since we were already in the market for drag radial tires, we decided to go up in size to a 275/50/17 on a pair of factory 17-inch GTO wheels. Nitto makes a tire that is very close to the advertised size-considering how important it is to get the right fit under a GTO, we went with the NT555Rs. But to make them fit, you will need to cut your rear quarter panels. Although it sounds worse than it really is, this procedure removes about 1/2 inch of much-needed space from the lip of the wheel opening. This area is often spot welded from the factory, so your car's structural strength is usually not compromised. Luckily, Jack performs this modification often, so he gingerly removed the sheetmetal, sanded it smooth and we then painted everything in the factory Torrid Red for a factory look.

Once the work was completed, we moseyed on back to the track in search of some reduced e.t. With five pounds of air pressure in the rear Drag Bags and the tire pressure set to 18 psi, we were ready to hit the staging lanes. In the burnout box, we performed a very thorough burnout to heat up the virgin Nitto NT555R drag radials. We then staged our Head Poncho and stalled it up to about 1,500 rpm, allowing it to flash upon launch. When the tree dropped, we mashed the gas and were blown away from the first numbers to show up on the Chrondecks-a 1.75 short time. With our eyes focused on the stripe and the hammer dropped, we crossed the line, went on the return road, and went to the timing tower to pick up our timeslip. From our previous best of 12.97 at 108.22, we were now looking at a 12.62 at 109.10 mph-that is an incredible three and a half tenths and a gain of nearly a full mph. We were floored with the car's performance and, obviously, are impressed with how easily a GTO picks up e.t. from slight mods.

Now that we've finished our first round of mods, we'll start planning our next assault. We will steer away from going over the edge and will not install a rollbar or turn it into a track-only piece. Our focus will center on dragstrip tomfoolery, but our Head Poncho will still remain a street-driven weekend warrior and we will not take away any of its virtues, including its fun-to-drive nature and romp-'em, stomp-'em attitude. Follow along and enjoy the ride.

Sources

Precision Industries
Whiteville, TN 38075
731-254-0055
http://www.converter.com
BMR Fabrication, Inc
Thonotosassa, FL 33592
JM Motor
Corona, NY 11368

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Our Newest Street/Strip Project Car Takes Command Of GM High-Tech's Offices
Vinnie The Hitman Aug 1, 2008

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