In the May '06 issue, we upgraded the clutch to a grippy Spec Stage 3 with a new flywheel on our supercharged '04 GTO, removing any doubt about the clutch system handling the increase in power. So now we have increased suspicions about the stock GTO driveline.
For example, the stock GTO driveshaft, though good at noise abatement, actually uses rubber joints to connect the halfshafts to the front and rear yokes. Yes, you read that right: rubber. With hard launches, the stock driveshaft won't last long, and the rest of the stock driveline isn't much better. Some rear halfshafts have failed on otherwise-stock cars with supposedly minimal abuse, and there have also been cases of the stock axle stubs shearing or twisting the splines in GTOs raced on the dragstrip.
Obviously, we don't want to take our blown Goat to the track only to pick up the pieces from the pavement. We need stouter parts. Luckily, BMR Fabrication has designed an entire driveline upgrade package patterned off its racecar, which had experienced all of the failures we've mentioned. Through careful R&D and testing on the company's 10-second Goat, BMR developed a "Bulletproof" driveline. Components include a Harrop differential cover and upper mount for $429.95 (PN DC001), and from BMR, billet stub axles for $459.95 each (PN AS001-L and AS001-R, left and right respectively), 300M halfshafts for $499.95 each (PN CV001), and a 3.25-inch diameter carbon-fiber driveshaft for $1,299.95 (PN DS001). The only thing left to upgrade is the differential itself, and those seem to do relatively well in most applications.
Follow along as we show you how to upgrade your '04-'06 Goat's driveline for longevity, performance, and perhaps even reduce that pesky wheel hop in the process!
Conclusion
Once on the street, we noticed an immediate increase in rear-end stiffness under acceleration. Wheel hop was significantly reduced on hard launches, and we didn't have to worry about dental fillings falling out when launching on concrete with a quick clutch dump. The BMR setup is just what the doctor ordered for our pumped-up Goat, and the piece of mind it provides is well worth the cost. If you have a heavily modified GTO, BMR has a driveline package with your name on it!
Raise and support your Pontiac safely. Remove the drain plug from the rear axle cover, and drain the differential fluid. Using a 5mm Allen wrench, unbolt the ABS sensors from each side of the axle. These units pick up wheel speed from a reluctor wheel machined into the outside of each stub axle. | 
Bolt a slide hammer to the axle stubs. If done carefully, you can use the stock bolts. A gentle tug should remove both axle stubs. | 
With a tall screw jack, support the bottom of the rear-axle center section. Place a block of wood between the center section and the jack to prevent marring the epoxy finish. Using an Allen-head socket and a ratchet, unbolt all of the halfshaft-to-inner-and-outer axle bolts. Take care to not lose the metal retainer plate that keeps the bolts paired up. Set them in a safe place to be used later. While these bolts are torque-to-yield, there are no reports of failure when reusing them. They're quite expensive, so if you're comfortable reusing them, go for it; otherwise order some from your local GM dealer. |