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.
One of the most common suspension items to replace or service on the 911 is the constant velocity, or CV joints that connect the wheels to the transmission. These bearings, packed in grease, get a tremendous amount of mileage through the years, and thus have a tendency to wear out after about 100,000 miles or so. One of the clear signs that the joints need replacing is the distinct sound of a clunk, clunk, clunk coming from the rear axle when the car is in motion.
In some cases, the boots that cover and protect the CV joints will be torn and need replacing. The procedure for replacing the boots is very similar to the procedure for replacing the entire joint. New boots should be installed each time a new CV joint is installed.
If you are planning on replacing both the inner and outer joints, then you should probably purchase a brand new axle. The new Lobro axle contains both the inner and outer CV joints, as well as the boots that cover and protect them. In addition, the complete axle is usually about the same cost as if you purchased just the CV joints and the boots. Plus, the entire assembly ships with everything installed. All you need to do is to bolt it up to the car.
The complete axle is also a good option for replacing the CV joints on the late model 911 1984-89 Carreras. The inner CV joints are an integrated part of the stub axle, and are not available separately. The Carrera axle ships with the two CV joints and the stub axle as a simple replacement unit.
The first step is to jack up and raise the car off of the ground (see Project 1 for details). You don't need to remove the road wheels, although it is recommended that you do so in order to gain yourself some more working room. The next step is to start removing the bolts from the CV joints. Start by making sure that you have the correct tool. On some early 911s, the bolts need a six-point star pattern removal tool to loosen them up. On some others, the bolts used only a standard Allen hex pattern. Either way, you must have the correct tool for the removal task, or you might strip out the CV bolts. If you do strip out the bolts, the only way to remove the bolts is to grind them off, which is not a fun task. Sometimes on the early cars, the bolts have been replaced with ones that are easier to remove. For instance, it's common to find that the bolts on the early cars have been replaced with ones similar to the simpler hex pattern. Either way, it's recommended that you use a socket tool to remove the bolts and reinstall the bolts, since you will have to torque them with a torque wrench when you are finished.
In order to gain access to the CV bolts, rotate the wheel of the car until you can clearly get your socket wrench on the bolts. Then, pull the emergency brake and place the transmission into first gear. This will allow you to loosen the bolts without having the axle spin. When you have removed all the bolts that you can from this angle, release the brake, take the car out of gear, and rotate the wheel until you can reach the next set of bolts. If you are planning on removing the whole axle by removing both the inner and outer joints, then work on the bolts on both the inner and outer joints at the same time.
Once you have the CV bolts disconnected, it's now time to separate them from the transmission or the stub axle. On the early cars, there are roll pins that help align the CV joints with the flange. Using a small screwdriver, poke into the CV joint seal that is located between the CV joint and the transmission. With the emergency brake released and the car out of gear, rotate the wheel around as you gently pry the two apart. On the later cars, there is no pin holding the joint and the flange together, so they should simply come apart. Make sure that you wear safety glasses when working underneath the car. You would hate to have an axle fall on your face.
If you are replacing the entire axle, or the boots on both sides, simply remove the axle and take it over to your workbench. If you are only replacing one boot or one CV joint, you will have to continue to work underneath the car. The CV joints are held onto the axles using a large circlip. Remove this circlip, and the joints should come right off. In general, it's a really bad sign if large balls from the bearing start falling out. That's a clear indicator that you need to replace the joints. If you are reusing the joints again, make sure that you carefully place them in a plastic bag, and avoid getting any dirt or grime in them. Even a crystal of sand or two accidentally placed in the joints can help them wear out prematurely.
Once you have removed the joints, then the replacement of the boots should be easy. Simply disconnect the small clips that hold the boot to the shaft and slide it off. The new ones are simply installed in a reverse manner.
When installing the new CV joints, make sure that you pack them with plenty of CV joint grease before you install them on the car. Also make sure that you place plenty of grease in and around the boot. Move the joint in and out as you insert the grease to make sure that you get it well lubricated, as the new CV joints do not come pre-greased. When ready, place the new boot on the axle and then place the CV joint on the axle. Reattach the circlip so that the joint is attached to the axle.
Now, insert the CV joint back into either the stub axle flange or the transmission flange, making sure that you don't forget to install the CV joint gasket. Pack a little more grease into the recesses of the flange before you remate the joints together. Finally insert the bolts, and tighten them up. Using a torque wrench, tighten up the bolts to 83 N-m 61 ft-lb for cars with four M10 bolts on the flanges, and 47 N-m 34 ft-lb for cars with six M8 bolts on the flanges. For 1965-68 911s, tighten them up to 47 N-m if you have the Nadella axles M10 bolts, or 43 N-m if you have the early Loebro CV joints M8 bolts. You may need to drop the car down onto the ground in order to tighten to this spec without turning the wheels.
Once you have the entire assembly back together, take the car out for a drive, and check the rear for noises. All should be smooth and quiet, and the boots should no longer leak.
Shown here is a complete axle for a late model 911 Carrera (1985-89), a CV joint for the 911SC, and a CV boot for an early 911. On these later cars, the outer CV joint is not available separately, but must be purchased as a complete axle. This is because the joint is integrated into the stub axle and cannot be separated. If the boots are damaged and leaking, then you should replace them, because dirt and debris can find their way inside.
The four CV joints are located in the rear of the car, attached to both the transmission flanges and the stub axles on the trailing arms. It's recommended to replace the joints in pairs: either both of the inside ones or both of the outside ones. Chances are if one of the joints is showing signs of wear and deterioration, then the other three will not be far behind.