How to Replace a Front Universal Joint
The front universal joints are designed to transmit rotational power from the gearbox to the front wheels in such a way that wile driving, the wheels and their steering spindles are able to pivot in order to allow the car to steer. Thus, the universal joints can be described as articulated shafts and must be very strong in order to withstand the hardships of driving. For this reasons, when they show sign of wear,replacing themis most important and can be done either by a specialised shop or by a "Do-It-Yourself" owner with some knowledge and one free afternoon.
This short article is intended to provide an insight and some general guidelines about universal joint replacement, however, depending on your particular car there might be differences between the procedure described here and the actual situation on your car's universal joints. Therefore, it's always a good idea to order a repair manual for your car, to read dedicated internet forums to consult with other owners who attempted this replacement, and in general, to thoroughly research all the aspects of the job involved. Knowing this, you can proceed at replacing the universal joints (you should do one side of the car at a time):
First you will need to remove the front wheels. Loosen the lug nuts while the car is still standing on the ground, then jack up the car by it's recommended jacking points and place axle stands immediately. Never attempt to work on a car supported only with the jack. With the car jacked up, remove the lug nuts and both the wheels. It is generally recommended to replace both universal joints, left and right, even though you it might appear that only one is failing.
Next, you will have to remove the brake disk- this is usually held in place by a large nut secured with some sort of locking element: a cotter pin, a small bolt and nut, a second large nut, and so on. This depends from car to car. Remove the locking element, and then the large nut. You might have to get a helper to push the brakes in order to hold the braking disk firm while removing the nut. This usually requires a lot of force and a big socket wrench.
Once the disk nut is removed you can loose the bolts holding the brake calliper and remove it as well. Do not let it hanging by the flexible brake line. It's best to make some sort of wire hook or hanger and hang the calliper in such a way that it won't obstruct you from working, but also won't stretch the brake line. After that you will have to remove the disk rotor. Usually it should come off easily, however, a specialised extractor might be in handy, or you can try to tap it off with a large rubber hammer, or with repeated short and light taps from a metal hammer. Do not tap with the metal hammer on the braking surface of the rotor, only on the sides, and use gentle force in order not to damage anything.
By this point, if your car has an A.B.S. system you should look through the back of the steering knuckle and notice a small slotted rotor and an electrical sensor. You will have to unbolt the sensor and set it aside, hanging, but take care into not damaging it, or it's wires.
Now you're ready to pull out the hub axle assembly containing the universal joints. Look at how it's attached to the steering knuckle - again this depends on the make and model of your car - sometimes there is some kind of cover or flange held in place by large bolts behind your steering knuckle, other times, the outer race of the hub axle is pressed into the knuckle. Again, you might want to use light taps with a hammer, but be careful not to damage anything. Use a lot of penetrating fluid, if necessary. The gearbox end of the hub axle will usually slide off from it's splines inside the gearbox.
Once you remove the hub-axle, take it on a vice and inspect the universal joint. It usually resembles a thick cross shaped element, held in place with cir-clips, or other securing elements. Remove those and install the replacement universal joint. Re-assemble the axle and proceed to install it back on the car. Installation is the reverse of the removal operation. Be careful not to omit anything, and torque all the bolts to spec - that's why the car's user manual comes in handy, as well as a torque wrench. As long as you have the universal joint replaced, it might be a good idea to replace the brake pads and disks as well, if necessary. Once everything is in position, inspect once more the hub axle, the joints, the calliper, the A.B.S. sensor, and everyhting else you've worked on, and if everything in order, proceed to the other wheel.
