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U Joints - Installing New Universal JointsEliminate Driveline Vibration for Less Than $100
Most rear-wheel-drive cars and trucks will need the universal joints replaced at least once during their service life and possibly more often if it's a high-performance vehicle or equipped with a manual transmission. U-joint life can be extended with periodic maintenance by greasing the zerk fittings (if so equipped), but general abuse such as popping the clutch and full-throttle power shifts will shorten U-joint life considerably.
When to Replace
How do you know when it's time to replace U-joints? The telltale signs are a "clunk" in the driveline when you engage the clutch or move the shifter from Park to Drive with an automatic. That "clunk" usually indicates one of two problems: worn U-joints or too much pinion gear lash in the rear end. It's fairly easy to determine between the two by grabbing the driveshaft and trying to rotate it back and forth. If the pinion yoke has a lot of rotation, it's probably gear lash. If the driveshaft has play and rotates, it's probably worn U-joints.
Another telltale sign of worn U-joints is driveline vibration at higher speeds. The vibration usually starts at approximately 50 mph and increases proportionately with speed. At freeway speeds it can seem as much a "growling" noise as a vibration. If you are still unsure, have a mechanic check them out with one of those free 20-point safety inspections.
Any thorough restoration should include replacing U-joints, simply because they are fairly inexpensive to replace, and it will provide you with an opportunity to properly detail the driveshaft. It's a great Saturday afternoon project. There are a couple of tips to make the job easier and will make the repair longer lasting. First, purchase or rent a U-joint pressing tool. It will make the job go much easier and faster, and you won't damage the driveshaft trying to "pound" out rusted and stubborn U-joints. Secondly, purchase the highest quality U-joints you can find. Many inexpensive U-joints are inferior and won't hold up to the high impact loads associated with most musclecars.
We purchased a U-joint installation tool on sale from Harbor Freight for approximately $23. It's a rugged tool that also works on ball joints, and it paid for itself on this one job. The U-joints that we used are from Federal-Mogul and come with zerk fittings. They cost about $30 for the pair at our local auto parts store. We also sanded our driveshaft smooth and coated it with Eastwood Company's Spray Gray (Part No. 1258Z) for a great look. Follow along as we perform this U-joint replacement on our '69 Buick GS 400. The results were great!
Eastwood Company, www.eastwoodcompany.com
Harbor Freight Tools, www.harborfreight.com