Modified Mustangs & FordsHow To Drivetrain
Custom Ford Driveshafts For Increased Power - Shaft
If You're Going To Step Up The Power, You're Going To Need A Custom Driveshaft
Driveshafts just don't give us that eye washing thrill of a powerful new engine, a fresh coat of paint, or a striking set of wheels. But they're just as important as horsepower, paint, and rolling stock. We don't give driveshafts much thought when we're planning our projects. And unless the driveshaft or a universal joint fails, it just isn't going to get much of our attention.
It's good practice to think about the driveshaft and universal joints when you're planning more power underhood. As horsepower and torque increase, the demands on a driveshaft, universal joints, and yokes rise accordingly. If you are stepping up to a 9-inch rearend, the difference in driveshaft length is probably going to mandate a new driveshaft anyway.
How do you order a new driveshaft, and what do you need to know before doing so? Before we get into driveshaft fabrication, let's look at driveshafts, universal joints, and yokes.
There are three basic types of driveshafts available for classic Fords: steel, aluminum, and carbon fiber (composite). Classic Fords and Mercs were fitted with steel driveshafts from the factory. Some were of a two-piece design, with an outer shaft and an inner shaft separated by a rubber vibration absorber. This design was common with automatic transmission cars to improve driveline smoothness. Manual transmissions were a single steel tube shaft only. Some applications were fitted with a slip-yoke/harmonic balancer design, also intended to absorb vibration. There were many variations in vintage Fords to begin with.
In any case, be it one-piece steel or two-piece, we suggest replacement of your factory driveshaft with a new one-piece steel shaft for your vintage Ford. We make this suggestion not to help these folks sell driveshafts, but for you to get into current universal joint technology, availability, and installation. Many original Ford driveshafts use inside snap-ring universal joint cup retainers. These clips have been known to fly out (if improperly installed), causing the cup to fly out, which throws the driveshaft off center. If this happens at 70 mph, it can be catastrophic. When a driveline company builds you a new shaft, it uses the outside snap ring cup retainers, which are more secure and safer. But like the inside snap ring, they mandate close attention to detail during assembly. Another issue surrounding the inside snap-ring universal joint is availability. They are harder to get these days from auto parts stores for classic-style driveshafts.