A few weeks ago we were washing the A6 when we noticed grease on the one of the front wheels. Upon further inspection we soon realized it was a symptom of a failure we knew all too well. The outer axle boot had torn from stress, spewing grease all over the wheel and suspension components. While not a dire malfunction, the problem does need to be addressed as soon as possible. A torn boot can allow road debris and other damaging materials into the CV joint it normally encases. If left too long, the grime from the road can destroy the ball bearings in the joint. Also the loss of grease can cause too much friction and damage the bearings as well. Both of these outcomes can mean rebuild of the joint or in particularly bad cases, a total replacement of the axle. (With OEM axles for the C6 A6 being over 700 dollars, it wanted to avoid this greatly) A boot rebuild kit is available from most car part suppliers, ours was fifty dollars or so, much better than the alternative. Good kits will come with a new C ring, both boot clamps and a new axle bolt. (These are one use bolts, do the high stress levels they endure) Obviously a new boot should be included as well. We chose to go with an OEM kit, which meant a higher cost, but less worry about the quality of the rubber. The tools for this job on most Audis are pretty basic, however you will need a triple square bit for the axle to trans bolts. (Typically a M10) And you will need a large hex head socket. (Typically 17mm, although our replacement bolt was 19mm) Other useful tools to have ready would be a long ratchet extension bar, for the axle to trans bolts. As well as a good vice for separating the C ring. The removal of the axle is simple enough, provided that the pinch bolts for the upper arms and tie rod end are not seized. We started by cracking the axle bolt, which is normally around 130ftlbs. To do this we used a 4 foot breaker bar and some elbow grease. Some things to note:
- Make sure the hex head is seated all the way in, to avoid striping the head.
- Make sure that you are actually turning the bolt and not just the head.
- Make sure you have the wheel still on the car, with the center cap out in order to stop the hub from free spinning.
- An alternate to the tire method is to have the brakes depressed to hold the hub in place.
Next we pulled the pinch bolts for the upper suspension. (Luckily these came without a fight) With the top of the spindle free, and the axle bolt out, we were able to move the spindle out of the way and remove the six triple square bolts holding the axle to the transmission. Then we slid the whole axle out the car and got ready to replace the boot. The first thing we did with the axle on the bench was clean it up, then we snipped the one use clamps from both ends of the outer boot. With these out of the way, we cut the old torn rubber boot off, exposing the bearings and CV joint. (Warning, it’s messy) The next step was to separate the outer joint from the spline shaft. This is where it got tricky. Normally the way to do this would be by using the old axle bolt. Driving it in all the way should push the joint off on most cars…unless the axle is hollow. In our case, the axle was indeed hollow, which made the standard method no good. This is where a good vise comes in handy. We mounted the axle in the vise, and using a soft metal chisel and hammer, we tapped the inner bearing race to free the joint. Once the joint was free, we could slide the new boot and smaller clamp into place. With that done, we packed the new boot with fresh grease (also provided in our kit) and replaced the old C ring. We also put new grease on the bearings as well. To reinstall the CV joint, we VERY CAREFULLY lined up the splines and tapped the joint back into place. It helps to reinsert the old axle bolt and hit that, so as not to mar the outer spline head. This doesn’t take much force, so if it’s not working, double check the alinement of the splines. Once the axle was back together, we tightened down the boot clamps and began the reinstall of the axle. This is the reverse of the removal, so it should not be too hard. Get the axle onto the trans first and then line the splines up with the hub. Drop in the six triple square bolts and then the axle bolt. Torque the axle bolt to the right spec and go another half turn. Reattach the spindle to the upper control arms and tie rod, and torque down the pinch bolts to the correct spec. Make sure the wheel is on tight and take the car for a spin! That’s basically the job in a nut shell for most Audis. As you can see, it’s not too complex and can save you some money for other car parts. As always, do not attempt this unless you are qualified and comfortable doing so. Happy wrenching!
DIY Link: AUDI AXLE BOOT REPLACEMENT