2004 Pontiac GTO - Shifting Stability
Our ProCharged GTO made a whopping 444.5 hp at the rear tires after being tuned with a new Racetronix fuel system on a Mustang chassis dyno ("Fueling the Fire," March '06). This kind of power is great, but after a few hard launches, the stock clutch was getting ready to say "uncle" in a big way.
Not wanting to risk having to limp the car home from the track or the dyno (it actually slipped a smidge on the dyno during one pull), we decided it was time to investigate what kind of clutch would hold up to the abuse of a 500-or-so rear-wheel horsepower, 3,900-pound Pontiac.
Our search ended at S.P.E.C. Inc. with the suggestion that a Stage 3 clutch with the company's aluminum outer, steel-center flywheel would be more than adequate for our boost-breathing Poncho. According to David Norton, vice presi-dent of S.P.E.C. Inc., "The flywheel body is made of tempered aerospace-quality aluminum with a high carbon steel friction plate. The fric-tion plate is end-user serviceable and has fasten-ers that are hand tightened to exactly the same torque all the way around to eliminate runout. S.P.E.C. holds a 0.001-inch machine tolerance on the product. This means the clutch has aperfect mating surface, maximizing drive-ability and clamp, and the flywheel has a perfect balance for less stress on engine internals. The pressure plate is our newest offering, featuring a 360-degree CNC pivot. This means our pres-sure plates have a more even drop on the disc, more consistent diaphragm height, more con-sistent and higher clamp load without severely stiff pedal requirements, and do not require aftermarket hydraulics."
The Stage 3 carries S.P.E.C. PN SC093 and a suggested retail price of $449, while the complementing aluminum outer steel friction surface flywheel has PN SC75A and a price of $399. When you order both pieces together, they come in a matched and balanced pair for a simple bolt-in installation.
Another issue we faced with our GTO is the stick-in-the-mud feeling the stock shifter provides. Ask any six-speed GTO owner with the stock shifter, and we're sure they'll tell you they have missed a gear once or twice due to the disconnected feeling of the remote design. The solution for our rubbery shifter came in the form of a GM Motorsports (GMM) RipShift shifter from Speed Inc. The RipShift carries part letters RIPSHIFT and a price of $299.99. While it may be a bit on the pricey side, the Australian-made shifter does have quite a lot to offer late-model GTO owners. The aftermarket shifter of choice for nearly every Australian enthusiast with a six speed Holden, the RipShift offers a tight, precise gear pattern with considerably shorter shifts, and it even retains the stock shift handle location. RipShift's sturdy machined-aluminum base with integrated heavy-duty centering springs make the 2-3 and 3-4 shift a breeze-simply push or pull! The RipShift also features a steel shift lever to increase strength.
Follow along as we upgrade the clutch and shifter in our late-model Goat for more clamping power and a better overall shift quality.
Special thanks to Jon Schwenn, Ryan Bowman, and Shawn Sullivan.
On The Road And On The Dyno
With the clutch installed, it was time to endure a long, 500-mile no-WOT or hard-launch break-in period. It's also important to try and avoid slipping the clutch any more than necessary. The pedal feel is definitely considerably firmer, and the clutch did chatter quite a bit at the beginning of the break-in. While breaking in the clutch, we finally got to experience the GMM RipShift firsthand after hearing people rave about it. The RipShift is incredibly precise and feels as though you are shifting with a hammer-it's confidence inspiring. In addition, through the use of some relatively heavy centering springs, the shifter lines itself up for a 2-3 and 3-4 shift; all you have to do is push or pull.
After we had completed the requisite 500 miles, the clutch chatter was considerably reduced, and the pedal got a slight bit softer but was still quite firm. While it's a driveable clutch, it could get quite heavy in stop-and-go traffic; it's really a personal preference here.
For a lighter pedal feel, S.P.E.C. now offers a new Stage 3+ that holds 700 lb-ft torque with a full-faced disc but drives like a Stage 2+. The regular Stage 2 will hold the power the GTO makes right now, but we are preparing for the future.
While we did expect to see a slight power increase due to the lower rotating mass of the S.P.E.C. Stage 3 assembly, the results were actually quite impressive.
On Vector Motorsports Mustang chassis dyno, our GTO put down a solid 452.7 hp. What's significant, however, is that in its previous pull prior to the clutch, it put down only 444.5 hp. We freed up over 8 hp by switching to the lighter, more durable S.P.E.C. Stage 3 clutch. Torque remained mostly unchanged from 393 ft-lb to just over 394. All testing was done in 85-90-degree ambient temperatures with intake air temps well over 100 degrees-not exactly conditions that will make a supercharged car shine. So not only did we get the added benefit of a clutch that can handle considerably more power, but also one that actually freed up more of it.

Photo Gallery: 2004 Pontiac GTO - High Performance Pontiac Magazine

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