The loud "clang" noise coming from the driveshaft in an accelerating vehicle likely comes from the driveshaft universal joints. Noise is generated because the U-joints are severely worn and moving around within the driveshaft/yolk assemblies. This is extremely bad and potentially dangerous. When there is noise, the U-joints are shot and need to be replaced. One good launch at the dragstrip will likely destroy the clanking driveshaft assembly. If there's not a driveshaft safety loop, a nasty crash could occur if the U-joints fail.
Because universal joints are among the most overlooked hop-up amongst car enthusiasts, chances are good that most are stock and have never been replaced. Stock U-joints are medium-duty units at best. They were not designed to handle the rigors of street/strip use. Upgrading your driveshaft with new U-joints is a step in the right direction. But what you should really do is upgrade to heavy-duty U-joints that can handle the hard-launching abuse inflicted by today's high-horsepower Ford machines.
Here, we follow along as the driveshaft experts at Wenco Industries show us how to install new heavy-duty Lakewood U-joints in a driveshaft assembly. This driveshaft wasn't making noise, but we wanted to replace the U-joints before they started acting up. Good advice is to have the driveshaft balanced and checked for straightness while it is out of the car. And this is exactly what Wenco Industries did to ensure that our driveshaft performs properly for years to come.
And one other thing. Some Ford automatic driveshafts were of a two-piece rubber-cushioned design made to absorb vibration. The thing is, after 30 years of use, many of them are not suitable for continued use. If your two-piece driveshaft has deteriorated and is nonserviceable, a replacement driveshaft may be in order. In the months to come, we will show you how to have a new driveshaft made from scratch.