GTO 3.5 aluminum - rear yoke included 900HP, 7200RPM MAX.
The factory driveshaft in the GTO is the weakest part of the entire driveline. It's a two piece design that is only 2 inches in diameter and uses rubber mounts instead of u-joints. Not only do the rubber mounts contribute to wheelhop, they are notorious for failing on even slightly modified 6 speed cars.
Our heavy duty driveshafts are a one-piece design that use forged 1350 series u-joints. Each driveshaft comes with a cryogenically frozen front yoke and a custom machined 300M billet pinion yoke adaptor (shown below). NOTE: Due to the physical size of this driveshaft, the factory exhaust may require some modification. Most aftermarket exhausts tested do not have clearance issues. Steel driveshafts not recommended for 6 speed cars.
There are a few important factors to consider when choosing a driveshaft. The main two are driveshaft rpm and engine horsepower level and sometimes they go hand-in-hand. Each driveshaft is limited to a fixed operating range based on the driveshafts' diameter and length. Beyond a certain rpm, the driveshaft will begin to deflect in the middle, creating excess harmonics and vibration eventually leading to failure. This rpm is technically called the critical speed of the driveshaft. It is very important that you choose a driveshaft that is rated properly for your application, a driveshaft that fails at critical speed can be catastrophic.
DETERMINING CRITICAL SPEED
Driveshaft rpm is identical to engine rpm when the transmission is in 3rd gear for automatics or 4th gear for manuals. These gears are both 1:1 ratio. Overdrive increases driveshaft rpm (at a constant engine rpm) so keep that in mind when choosing the proper driveshaft. As an example, lets say you want to use our 3 aluminum driveshaft rated at 450 hp and 6400 rpm. The GTO has a 26 tall tire and 3.46:1 gearing. Basically, if the car could physically pull to the driveshaft limiting 6400 rpm , your top speed will be limited to 140mph in 3rd gear. Since driveshaft rpm is relative to mph, this will be your top speed regaurdless if you are in 3rd gear or overdrive. The bottom line is you would need to upgrade to a larger diameter driveshaft if your horsepower level exceeds 450 or you wish to drive faster than 140 mph.
The steel 3 shaft has a higher horsepower rating but the rpm limitation is the same. Most cars with head and cam packages have extended rpm ranges so even though you may be safely within the horsepower rating of the driveshaft, you will begin to approach critical speed sooner. Keep this in mind also when choosing your driveshaft.
Basically the 3.5 aluminum driveshaft and the 3.25 carbon fiber driveshaft both have high enough horsepower and rpm ratings that most cars will not ever exceed them. The main drawback to both of these is physical size. Both require shimming the differential down in order to create enough tunnel clearance for the shaft. We provide these shims with both of the larger driveshafts.
About BMR Suspension:
BMR Fabrication specializes in the design and manufacturing of high quality aftermarket suspension and chasis products for Ford and GM vehicles. Products include: swaybars, a-arms, lower control arms, shock braces, subframe connectors, drive shaft loops, pan hard bars, torque arms, crossmembers, and more.