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.
Driveshafts
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.
From left to right are the...
From left to right are the three basic types of drive shafts available from Inland Empire Driveline: steel, aluminum, and composite. Composite is the shaft of choice when you're going to throw a lot of power at the rearend. Aluminum driveshafts can take up to 500 hp. Steel shafts can take even more depending on which tube size and universal joint you choose.
Aluminum driveshafts offer...
Aluminum driveshafts offer reduced weight and less rotating mass. The weight advantage is what makes the aluminum shaft desirable. The 3.0-inch aluminum shaft with a .125-inch wall thickness will take up to 500 hp. Outside tube diameters of 3.5 and 4.0 inches are also available.
Opting for a steel driveshaft...
Opting for a steel driveshaft is going with the solid and reliable. Steel shafts can tolerate greater amounts of torque better than aluminum shafts, depending on wall thickness and tube diameter. Inland Empire Driveline can steer you straight on sizing.
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.
Composite driveshafts look...
Composite driveshafts look decidedly different than their conventional steel or aluminum tube counterparts. Composite shafts are carbon fiber wrapped up in a liquid resin that, when it cures, is super strong. What's more, it is much lighter than the aluminum shaft. If you're building a show car that's going to have mirrors underneath, the composite shaft is a showstopper. If you are going racing, it will take darned near anything you can throw at it.
This is a two-piece, steel-around-rubber-around-steel...
This is a two-piece, steel-around-rubber-around-steel tube driveshaft-original equipment in classic automatic transmission-equipped Fords and Mercurys. It's a good idea to replace this type of driveshaft with a steel or aluminum shaft for safety and security.
You will find this universal...
You will find this universal joint on older Fords, where the caps are tied to the different yoke with bolts instead of U-bolts. This is a Spicer 2.5R x 2C joint.