Where could this knocking sound come from on a car with a brand new axle?

Dear Car Talk

Dear Car Talk | Mar 01, 1995

Dear Tom and Ray:

I would guess that untyped letters are put on the bottom of the stack. How about good, large writing? So far, so good. Still with me? I have two 1986 Hondas. One is a hatchback, and one is a four door, but they both have the same problem. On turning left, there is a continuous knocking sound. It's more pronounced at lower speeds. My mechanic replaced the left front axle on the hatchback, but the noise continued. We're not going to do anything to the four-door until we figure it out on the hatchback. What should we do next? Sure hope you have a clue.

RAY: Well, you gave us one clue, Dick. It's not the left front axle.

TOM: Your mechanic believes it's a constant velocity (CV) joint, which is part of the axle assembly. And I think he's right. But the location of a CV joint noise can be very elusive. And in our experience, a bad CV joint noise that appears during a left hand turn is usually coming from one of the RIGHT front CV joints.

RAY: Why does a joint on the right make noise when you turn left? Well, when you turn left, you shift the weight of the car to the right side and impose a greater load on the joint. Plus, the angle of the joint's operation changes, and that combination causes the bad CV joint to clack.

TOM: Have your mechanic replace the right front axle, and I'll bet your noise disappears. And while you're there, have him check the CV boots (the rubber coverings around the CV joints) on both of your cars. Torn boots that lose their grease are the first step toward bad CV joints, and by catching torn boots early and repairing them, you may save yourself another axle replacement later on.

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