This article is one in a series that have been released in conjunction with Wayne's book, 101 Projects for Your Porsche 911. The book contains 240 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Porsche 911 owner's collection. See The Official Book Website for more details.
The design of the 911 suspension is similar to the design of a MacPherson strut except for the fact that the 911 uses torsion bars to spring the suspension load versus a coil-over-shock system. One of the principle components of the strut design that the 1969-89 911 uses is the ball joint. This joint, located at the bottom of the strut, helps the entire assembly pivot and rotate as the steering turns, and the suspension rides up and down. Needless to say, this critical component can wear out over time, and should be replaced every 100,000 miles or so or if the front suspension is beginning to feel a little wobbly.
The first step is to remove the pin that holds the ball joint in place. This pin is inserted into the strut, and needs to be pounded out with a large hammer. Sometimes this pin will be heavily rusted, and will need a significant amount of force to remove. If the pin is completely rusted in the strut, you may have to carefully drill out the center of the pin. In most cases, this won't be necessary, but with rusty cars you should expect the worse. Be careful when you are hammering on the end of the pin that you don't damage the threads, or the pin may need to be replaced. Place a nut on the edge of the threads to protect them from the blows of the hammer. It's also wise to use a punch or extension to hammer on, since you don't want to miss and hit your caliper or your strut. Make sure that you drive this pin out before you remove the castellated nut from the bottom of the joint, otherwise the strut will be hanging loose, and it will be difficult to keep steady.
The next step in replacement is to remove the small locking washer that is attached to the bottom of the ball joint. Take a set of needle nose pliers, pull out the cotter pin from the bottom of the ball joint and remove the washer. Now, remove the large castellated nut that holds the ball joint to the bottom of the strut. There are a few methods of doing this. The best method is to use a breaker bar or impact wrench and a ball joint nut removal tool, which is specially designed for removing this nut. Another method of removal is to use a large hammer and chisel, however this method can result in damaging the castellated nut. You can also try using a large pipe wrench to get a good grip on the nut. A fourth and more destructive method involves cutting it off with a Dremmel tool, and should only be attempted if the first methods fail miserably.
After the pin and the castellated nut have been removed, tap the ball joint out of the strut with a hammer. Make sure that you clean out any rust or debris from the inside of the hole where the pin is inserted and the hole where the ball joint is inserted. Spray a little bit of WD-40 in there to assist in the installation process.
The new ball joint should be positioned so that the cutout wedge in the shaft is facing the hole that accepts the pin. Gently tap the ball joint up into the strut, making sure that the wedge is somewhat aligned with the hole. Now, tap the pin into the strut. It should go in pretty smoothly, and it also should align with the ball joint wedge as it goes in. Replace the nut and washer on the opposite site of the pin, and tighten the nut until the back of the pin is almost flush with the strut. Reinstall this nut and torque to 45 Nm (33.1 ft-lbs). Make sure that you replace the locking washer and retaining pin at the bottom of the ball joint. The large castellated nut on the bottom of the ball joint should also be replaced if it was damaged.
I recommend that you perform the replacement on one side, complete the job, and then move and do the replacement on the opposite side. In this manner, you can check your work and refer to the side of the strut that you haven't disassembled for reference.
Shown here are a new ball joint, ball joint pin, and the tool required for removing the ball joint. Sometimes, the ball joint can be removed without the tool, but chances are you will damage the large castellated nut that holds in the ball joint. I recommend using a new pin if you experience difficulty removing the old one. Very often, these will rust into place, and become very difficult to remove.
After the spring clip is removed, you can attach the tool to the bottom of the ball joint for removal. Make sure that you use a very long breaker bar, as these nuts have a tendency to rust in place and can become very difficult to remove. The arrow points to the ball joint pin, which can also be very difficult to remove. Use a large hammer and a punch to drive the pin out of its location. If the pin becomes damaged in the process, make sure that you replace it with a new one.