The way you describe it sounds like a worn outer cv joint but that is not as common as it was 20 years ago and certainly not common at 78,000 miles. The exception would be if the rubber boot is torn and the grease sprayed out. Water and dirt will get in too and tear up the precision marbles and grooves. One outer cv joint has finally become noisy on my '88 Grand Caravan after 235,000 miles and two torn boots. Newer ones like yours should last even longer. It starts as a light clicking noise when turning and accelerating, then becomes more of a crunching sound as it gets worse.
If you want to try to diagnose this yourself, consider asking for a "Chassis Ear" at an auto parts store that borrows or rents tools. It is a set of six microphones, a switch box, and headphones. You clip the microphones to suspect points, then drive around while listening with the headphones. You can move the microphones around to zero in on the source of the noise. Be aware that many mechanics have never seen or even heard of this tool. Suspension and alignment mechanics use it to find rattles, squeaks, and other noises. The original model used six wired microphones but the newer model has four wireless ones. You can strap one of them right onto the half shaft next to the suspect outer cv joint.
Worn cv joints will make a repeated clicking as long as you're doing what makes it make noise. There is a different symptom that WAS real common years ago among one model. That was a single click when you accelerated forward, then it would make a single click when you backed up. The click would never occur twice going in the same direction; only once backing, then once going forward. That was caused by a loose axle nut. The fix was to remove the wheel, then the cotter pin and retighten the nut with a click-type torque wrench. The torque value, (tightness), is critical for the life of the wheel bearing assembly. By working loose the splines on the axle shaft would knock against the splines of the hub each time the direction was changed and the car was accelerated a little. Usually one re-tightening was all that was needed. If you're hearing multiple continuous clicks, the axle nut is not the cause.
The next approach is to have the steering and suspension systems inspected at a tire and alignment shop. Ball joints and outer tie rod ends can cause clunking noises under various driving conditions but those won't be continuous. There has been some problems with outer tie rod ends so those should be inspected periodically anyway.
Tuesday, September 4th, 2012 AT 9:24 PM