Most cars sold in the United States drive the front tires. It makes for inexpensive, easy-to-manufacture, roomy cars that get better gas mileage than the rear-wheel-drive alternative. Getting power from the transmission to the front wheels is a bit of a challenge though. That's what a halfshaft does. The two halfshafts have the simple job of transmitting torque to each of the front wheels. But that job is complicated by the drastic up-and-down motion of those wheels, the near-90-degree difference in lock-to-lock steering angle, and the requirement to attach to a stationary transmission.
In spite of this the halfshaft is a robust part with a reliable 100,000-mile life span. Still, like every stressed part, it eventually fails. The rubber boot on the wheel side is usually the culprit. It's easy to diagnose. If your car drives fine in a straight line but you hear a ticking noise from the outside wheel when you crank the steering wheel to lock, that shaft on the outside of the turn needs to be replaced. This may sound complicated, but the repair is actually easy enough to do in the driveway with a few hand tools. Replace the whole halfshaft, and don't attempt to repair the boot—it'll just go bad again. Buy a remanufactured halfshaft at a parts store, then take the old one in after the repair. They'll buy it back as a core and sell it to a recycler, who will rebuild it for resale. In all, the fix will probably cost less than a hundred bucks. Sweat the details though; nobody wants a wheel to fall off.
How Rzeppa Joints Fail
Constant flexing and heat causes the protective rubber boot to crack first, releasing the grease inside. Watch for a grease-covered inside rim. With the boot breached and the grease gone, dirt gets in, turning these machined parts into a gristmill of destruction.
The axle nut lives in the center of the front wheel behind the hubcap. (If you have alloy wheels, you've still got hubcaps; they're just tiny—about 2 inches in diameter.) Pry the hubcap off with a standard screwdriver. Buy a socket to fit the axle nut at a parts store, usually between 30 and 33 mm. You may need to remove a split pin holding the nut in place. With
the car on the ground use the socket and a breaker bar to loosen the axle nut . Jack up and secure the car, then remove the wheel.
Free Up the Suspension
Unbolting less is more here—free just enough to remove the halfshaft. In some cars you can pull the two bolts from the MacPherson strut , then fold the hub and knuckle down, and that's enough. For a double-wishbone suspension, the lower ball joint will need to be freed. Pull the split pin, loosen the castle nut, and hit the ball-joint mount until the taper bolt breaks free. Put the axle nut on for a few threads and tap the end with a hammer
Pull Off the Old Shaft
When loose, pull the Rzeppa joint free of the hub. You may need to twist and turn the hub and joint to make this happen. On the transmission side, use a flat pry bar between the joint and the transmission case  to gently pry the joint free. Rotate the halfshaft and pry at different points. Think of it as removing a socket from a ratchet. Some inner joints are bolted in place, so unbolt to remove.
Install the New Shaft
Replacement shafts are remanufactured old units, so make sure it matches the old shaft. Apply some white lithium grease to the transmission-side mounting surfaces and push the shaft into place. Use only your hands, and be sure it seats completely. If it puts up a fight, pull the shaft out, clean everything thoroughly, and try again. Work the wheel-side shaft into place and be sure it slides into the hub securely. Start the axle nut to hold it in place. Reassemble the disconnected suspension components and torque appropriately, then tighten the axle nut and mount the tire. Lower the car until there's a bit of weight on the tires and then torque the axle nut (see below) down—usually about 150 lb-ft of torque, but check your service manual . Finally, take the car in for an alignment. Things will be out of whack no matter how careful you've been, and a few bucks spent on alignment will make the car safe on the road and save your tires.