2004 Pontiac GTO Chassis Modifications - Back In Black: Part II

BMR's GTO strut tower brace...        read full caption BMR's GTO strut tower brace is a top-quality piece and is made from far thicker material than the stock item. Constructed from D.O.M. (drawn over mandrel) tubing, it comes standard powdercoated either red or black, or other powdercoat colors by special order. Retailing for $159.95, it carries part No. STB007. Decals and washers are included; the factory nuts will be reused.

Held side to side, the difference...        read full caption Held side to side, the difference between the factory brace (black) and BMR brace (red) is readily apparent. The stock unit measures only 1 inch in diameter and is made from tubing only 0.083 inches thick. BMR's is made from 1 5/8-inch tubing that features a 0.095-inch wall thickness. Despite this difference in size, weight penalty is minimal, with the stock brace weighing about 4 lb. and the BMR unit coming in at 6.8 lb.

The BMR brace is simply laid...        read full caption The BMR brace is simply laid in place and tightened down. A hefty 3/16-inch flange is used at the junction with the strut towers for maximum stiffness. The fit of the brace was perfect. We weren't expecting any problems, of course, as BMR is well respected for its top-notch build quality.

The completed brace installation...        read full caption The completed brace installation adds a whole lot to the look of the engine compartment. The red matches the spark plug wires and, of course, the gauges on our instrument panel. One really neat feature is that BMR will paint the brace your factory GTO color for an additional charge, which really looks trick on cars with unique colors like Yellow Jacket or Cosmos Purple Metallic.

BMR's lightweight skid guard,...        read full caption BMR's lightweight skid guard, part No. SG001, retails for $109.95. Cut from 0.160-inch aluminum, it weighs a scant 5.75 pounds (versus 15 pounds for the stock plate). Plus, this weight comes right off the front end of the car, exactly where you want to minimize mass on a rear-wheel-drive car. As the factory bolts will all be reused, no hardware is included with the kit.

In the last installment of our Pontiac GTO buildup, we added nearly 37 rear-wheel horsepower and 30 lb.-ft. of torque with some engine bolt-ons, including an air intake from LS1Speed, a cat-back exhaust from SLP Performance Parts, and custom engine tuning, also from SLP Performance Parts. These items brought power and torque up to 327.3 horses and 327.6 lb.-ft., respectively. Nitto Extreme Drag tires were also added to help put the extra grunt to the ground.

Since that time, the GTO has performed with hardly a hiccup. The sole issue encountered was that the engine would occasionally bump the rev limiter on either the 1-2 or 2-3 shift. This problem was easily solved by SLP, which lowered the shift points about 75 rpm using its LS1Edit software. That said, the car has stood up to quite a beating on both the street and track, and we've enjoyed every gas-guzzling moment of it. Now it's time to modify the chassis on our Phantom Black 2004 a bit before adding even more power to its LS1. The parts for this installment were chosen for their ease of installation and importance in addressing some of the GTO's more problematic design areas.

While the GTO comes from the factory with a strut tower brace, it really isn't much of a structural member. Pull it off and see; you can bend it using little more than your own two hands. Enter BMR Fabrication, a company that offers a myriad of components to improve the new GTO's chassis and driveline. Its strut tower brace is quite literally one of the easiest possible bolt-ons, as it involves only the removal of four nuts atop the strut towers. Not a touch of grease will grace your Goat-guiding hands. A post-installation test drive presented us with a noticeably stiffer feel, particularly over one-sided bumps. The difference is not a detriment to ride quality at all; it just adds a more well-built feel to the car. Curve carvers out there can certainly expect to love this product, as it serves to enhance the high-quality sport sedan feel that sets the GTO apart from other domestic cars.

Problem area number two: anyone who has performed an oil change on a GTO knows about the asinine piece of steel Holden has hanging below the oil pan. Obviously the pan needs a lot of protection, but come on, that thing weighs a ton--and makes an oil change a two-person job. With BMR's lightweight skid guard, just four bolts are involved in removing over nine pounds from the front end of the Goat. The only thing we could have wished for was some access holes in the guard for the oil drain plug and filter, but this would have compromised protection. After all, you never know what can come stabbing up at you from the road--and that oil pan hangs a good inch or so below the radiator support in front of it. Removing the BMR skid guard during an oil change is no big deal, as it is so much lighter than the O.E.M. steel piece. Nine pounds may not sound like that much, but anything helps in the quest to reduce our nearly 3,900-pound race weight.

Any owner who has gotten underneath their GTO for the first time has surely experienced a bit of shock and awe upon viewing the two-piece, rubber-isolated driveshaft, an item that screams, "Put on some sticky tires and break me!" BMR's driveshaft loop will give some much-needed peace of mind to any Goat owner. Though we are trying to keep this Pontiac a true "bolt-on" machine as of the moment, we had to make an exception here, as BMR's loop is a weld-in design. This is perfectly acceptable, though, as a bolt on-type loop for the GTO would involve cutting access slots in the frame or even putting bolts through to the interior of the car, which would be more of a pain than it would be worth (in addition to doing more permanent harm to the car's underside). Besides our personal desire to keep the driveshaft from damaging our GTO if and when it decides to let loose, with 13.20s in warm weather already lighting the boards, the mandatory NHRA loop cutoff of 12.99 was not too far away anyhow.

Last but not least, we wanted to address the wheel hop issue that many complain about with their 2004 GTOs. Manual cars experience more of a problem with this than automatics, and can even get the phenomenon on a hard 2-3 shift, which can purportedly almost get the car out of control. Truth be told, our automatic would only exhibit this hopping behavior around a sharp turn while coming from a dead stop, and even then, it would only be the outside wheel hopping due to the limited slip differential. To help solve this, SLP Performance Parts' bushing kits replace all of the stock rubber rear anti-roll bar ("sway bar") bushings with an attractive maroon polyurethane. Getting at the bushings atop the rear subframe is a bit of a hassle, as it involves partially unbolting and lowering said subframe, but the work is well worth the reward of added traction. A post-install road romp revealed that the wheel hop we had encountered previously no longer occurred. While we are not promising that manual transmission cars will have their problems cured 100 percent, we can tell you there is a good chance these SLP bushings will help quite a bit. We also did not notice any particular decrease in the quality of ride that one often expects from polyurethane bushings. This makes sense as after all, we replaced only the sway bar bushings; a swap of control arm bushings or the like would have certainly yielded a noticeable decrease in ride quality.

We come away from this second round of products on our project GTO very pleased with the outcome. All of the parts tested were of top quality and fit. Though no horsepower has been added this time around, a total of a little over $400 has improved this project car's handling and safety. Drag racer, road racer, or just plain street cruiser, any GTO on the road can benefit from that.

Only four bolts hold GM's...        read full caption Only four bolts hold GM's hefty steel skid guard in place; just be ready to catch it as you definitely do not want 15 pounds coming down on your foot (or head, if for some strange reason you do not have a lift in your personal garage). One can see that a skid guard is unquestionably necessary on the GTO as the front-sump oil pan hangs quite low. Not only is this protection important for not losing all of your oil thanks to a stray stone, but the cast aluminum oil pan is also a structural part of the LS1 engine, so you do not want even the tiniest crack in it.	BMR's skid plate simply lifts...        read full caption BMR's skid plate simply lifts into place and is tightened securely. While theoretically it is probably better to have a piece of steel here than aluminum, running over or into anything that is going to break BMR's plate is definitely going to break the rest of the car as well. Just don't jump your GTO off a pier, like in GM's infomercial (In slow motion, the front bumper flies off!).	Carrying part No. DSL009,...        read full caption Carrying part No. DSL009, BMR's NHRA-legal driveshaft safety loop is a must-have for anyone who drag races their GTO. Not only does the factory two-piece, rubber-isolated GTO driveshaft not instill the best of confidence for hard launches and shifts, but a driveshaft loop is mandatory anyway in all cars running 12.99 and quicker (13.99 with slicks). BMR includes grade 8 bolts and chrome-plated nylock nuts with its laser-cut, flat steel, powdercoated loop--all for $79.95. Expect only about a seven-pound weight penalty for such a tremendous increase in safety.
Since BMR's loop is a weld-in...        read full caption Since BMR's loop is a weld-in design, welding prep involves first lightly grinding the underside of the car to get a bare metal surface to weld to. Holden conveniently added floorpan bracing at just the right place for a driveshaft loop, so not only is the loop installation NHRA legal, but one need not even remove the interior carpet to weld. The corresponding areas that are to be welded on the driveshaft loop crosspiece must also be ground accordingly.	Here we weld using our $300...        read full caption Here we weld using our $300 MIG welder. Before commencing this operation, we were sure to fully assemble the loop and position it just right, and mark where the crosspiece should go. While BMR's alignment holes helped somewhat, we actually had to shift the crosspiece laterally just a touch from being centered on the factory floorpan holes, so that the upper part of the loop did not contact the side of the floorpan. Also note that the crosspiece is not symmetrical (due to different placement of the bolt holes on either side); care must be taken not to weld it in backwards!	After welding is complete...        read full caption After welding is complete and the crosspiece is allowed to cool, the loop simply slips over the driveshaft and bolts to the crosspiece. The two-piece design really eased installation as the driveshaft did not need to be removed at any time. After this, we painted the weld beads red to look nice and pretty, and to prevent the bare metal from rusting. For those who don't dig the red, the loop can also be had in black powdercoat or other colors by special order.
SLP offers two sets of sway...        read full caption SLP offers two sets of sway bar bushings for the 2004 GTO, and both are shown here. The eight round ones are its sway bar link bushings, which carry part No. 73006 and retail for $34.95 a set. The two others are the rear sway bar bushings, part No. 73005, which are priced at $24.95 a set. Both types are made from stiff K-Prene polyurethane.	The 2004 GTO uses some unusual...        read full caption The 2004 GTO uses some unusual curved pieces as sway bar links. These links connect the suspension arms to the sway bar, which rests atop the rear subframe. The inherent flex in the stock rubber bushings is visible even in this photo, so one can just imagine what happens to them when under the load of a hard launch or a hard corner.	Once the sway bar links are...        read full caption Once the sway bar links are unbolted from the car, the steel pins inside them must be removed. The best way to do this is by finding a bolt that is the same size as the pin and tapping it with a hammer. In the words of Sue Johanson of the Oxygen network, "some lubrication may be necessary." After this step is complete, the old rubber bushing halves are simply pulled out using pliers or a similar instrument. Then the new SLP bushing halves are installed and the original steel pins are reinserted.
In order to get at the bolts...        read full caption In order to get at the bolts holding the sway bar in place, the rear subframe needs to drop down a bit. To accomplish this, the differential carrier assembly needs to be adequately supported, here by a transmission jack and wooden block. Once the carrier is supported, the four bolts connecting it to the remainder of the vehicle above can be safely removed, and the jack slowly lowered to give adequate clearance for a wrench to fit between the subframe and the floorpan. You most likely do not need to unbolt the lower shock bolts, but if for some reason you do, be advised that lowering the subframe too far can start pulling on the brake lines, which you definitely want to avoid.	Once the subframe is lowered...        read full caption Once the subframe is lowered adequately, the rear sway bar can be unbolted (via only two bolts, one on each bushing bracket). Watch out for hydraulic jack creep while you have the sway bar out and are working on it, as the subframe can slowly lower itself and potentially start pulling on the rubber brake lines.	A little lube will likely...        read full caption A little lube will likely be needed to slip SLP's rear sway bar bushings onto the stock sway bar. These bushings do not need to be greased as the unique K-Prene material has its own lubricity built into it. Once the bushings are on, the stock brackets are placed atop them, the sway bar is snaked back into place above the subframe, and the two bracket bolts are tightened.
With the sway bar in place...        read full caption With the sway bar in place and the differential carrier bolted back up to the frame, the sway bar links are reinstalled between the sway bar and the suspension arm. SLP recommends putting the car on the ground and bouncing it a few times to settle the suspension before tightening the bolts to their final 20 lb.-ft.; we actually drove it around the block, which surely has the same effect.