Dear Tom and Ray:

How do you tell when a particular U-joint is bad? I have the classic squeaking noise of a bad U-joint, but my truck (a Ford F150) has three different U-joints. I tried prying each of them with a screwdriver, figuring there would be some "play" in the bad one, but I can't tell. -- Roland

Tom: You really can't tell with the driveshaft still installed. You have to take it out and flex the joints, Roland. That's often the only way to tell whether a U-joint is bad.

Ray: A universal joint (U-joint) is a connector that allows the driveshaft (or anything else) to operate at a variety of different angles. And to do that, it has to flex in two different directions.

Tom: And there are two ways U-joints usually fail. Over time, the little needle bearings can wear out, in which case the joint will loosen up and get too much "slop" in it. That usually causes a high-speed vibration, or a clanking noise when you shift from Drive to Reverse.

Ray: U-Joints can also fail by seizing. That happens when water gets into the joint and displaces the grease. And then the needle bearings rust, and the joint stops moving in one or both directions.

Tom: If a joint has failed due to slop, you often CAN tell by prying at it with a screwdriver. But if it's seized, the only way to tell is by removing the driveshaft and flexing it to see if it bends smoothly in each direction.

Ray: Two other suggestions, Roland. Once you have the driveshaft out, you might as well replace all three joints. If you're doing it yourself, they only cost about 10 bucks apiece, and it'll save you the trouble of removing the drive shaft again NEXT weekend.

Tom: And also, see if you can buy replacement joints with grease fittings. Some of them allow you to grease the joint, and that grease pushes the water out and makes the joint less likely to seize again.

Changing your oil regularly is the cheapest insurance you can buy for your car, but how often should you change it? Find out by ordering Tom and Ray's pamphlet "Ten Ways You May Be Ruining Your Car Without Even Knowing It!" To order, send (check or money order) to Ruin, P.O. Box 536475, Orlando, FL 32853-6475. You can also order online.

© 1998 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.

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