this tech article we will discuss replacement of the CV boots on the 1992-99
BMW E36 3 Series. Keep in mind that this tech article is not vehicle
specific but applies to all models in general.
are the CV boots? The CV boots are small rubber boots that fit over the CV
joint and the drive axles. What they do is hold grease inside the CV joint,
insuring that the joints stay lubricated and move freely. Over time, heat
and age can cause the rubber to dry out and crack. When CV boots crack they
can cause the grease to be thrown out of the boot due to the centrifugal
force of the drive axles spinning when you drive. When all the grease gets
thrown out, it can cause the CV joints to grind or seize. If a CV joint
seizes, it can cause it to lock up, and possibly break the axle. I have
experienced this first hand on my old Porsche 914. In that case, there was a
crack in the boot, which threw all the grease out, eventually causing the
joint to seize. When it seized, it broke the mounting bolts to the
transmission, throwing the axle upward, and then it broke the transmission
case where the starter bolted on. I had to get a whole new transmission
because of a cracked rubber boot. I was not happy.
prevent such disasters, itís important to periodically inspect the boots
for cracks or tears. If you find one, itís a good idea to go ahead and
replace all 4 boots at the same time. In this article, we will assume that
the CV joints have seized as well and need replacement. That said, hereís
how you do it.
replace the CV boots, we will need to remove the drive axles from the car.
To begin, we will need to first pry the center caps off the rear wheels
while it is still on the ground. Now look inside, you should see the drive
axle retaining nut. We will need to loosen this nut with the car on the
ground. This will help you gain enough leverage to get it off, as it is
torqued in excess of 150 ft/lbs. In many cases, it may be easier to simply
use an impact wrench. Get the nut loose but do not remove it.
Be sure to use plenty of penetrant spray such as WD-40 while
loosening the nut. This will prevent stripping or seizing.
letís jack the car up. First, chock the front wheels to keep them from
rolling while you have the rear wheels jacked up. Next, loosen (but do not
remove) the rear lug bolts. Now, use a floor jack and jack up the rear of
the car. Be sure to jack the car up on a re-inforced part of the body, such
as a crossmember or chassis beam. Be sure not to jack the car up on any
other part, as you could put a hole right through the bottom of the car. I
have seen Porsches in the past where jacks have punctured the floorboards. A
handy reference is Wayneís article on jacking up your BMW.
Once the car is firmly secured on jack stands, the next step is to
remove the lug bolts on the rear wheels and take the wheels off. Now, look
at where the drive axles are bolted onto the differential. There are six
Torx head bolts that hold each axle to the differential. Before you remove
them, itís a really good idea to clean them off to get any dirt of grease
out of the bolt heads. Any good brake cleaner should work perfectly. We
donít have to get them spotless, however just enough to where we wonít
have the Allen key from popping out. Itís also a good idea to hit the
bolts with WD-40 or good penetrating oil. Typically, I like to let the spray
sit overnight, to let the oil work itself into the threads. This will make
it much easier to remove the bolts, not to mention preventing stripping and
seizing when you hit them with the wrench. Now remove all the bolts. The
drive axles will now be free of the differential. Use a piece of rope or
stiff wire to hang the drive axles to the car and keep them from crashing
remove the axle retaining nut on the outside of the wheels and remove the
lock plate underneath. Now, to get the axles out of the car, we will need to
use a puller to push them out of the trailing arm hubs. Using the lug bolts
to secure the puller to the hub and then tighten the center bolt to push the
drive axle out does this. Once free, remove the drive axles from out of the
car and take them to a workbench or other suitable work area.
look at the drive axles, you will see the rubber boots on either end of the
axle. Remove the clamping bands that hold the CV boots, and then cut the old
boots off the CV joint and the drive axle. We must now remove the CV joints
from the axles in order to put the new boots on. Start off by looking at the
ends of the axle that bolt up to the differential. This is the inner CV
joint. There is a metal cover over the end of the CV joint. Pry this cover
off. You will now see the inside of the CV joint. Wipe off the grease from
the center of the joint and you will see a circlip holding the CV joint onto
the drive axle. Remove this circlip. Now support the inner hub inside the CV
joint and using the puller, press the drive axle out of the CV joint. Be
sure not to let the inner hub rotate more than 20 degrees in any direction,
otherwise, the ball bearings will fall out of the CV joint, and you will
know true frustration trying to re-install them.
in mind that the outer CV joint cannot be removed from the axle. If this
joint ever goes bad, you have to replace the whole axle, (hence, why itís
important to check for broken CV boots!) However, we do have to remove the
inner joint to replace the outer boot.
you have the inner joint off, clean all excess grease off the drive axle and
slide a new CV boot down the axle shaft. Before you fit the boot over the
joint, put about a handful of wheel bearing grease inside the boot and
inside the CV joint. This grease will keep the CV joint lubricated and also
protect the boot as well. Now fit it over the outer CV joint and use new
clamping bands to hold it in place.
take another CV boot and slide it halfway down the axle shaft before you
install the new inner CV joints. Installation of the new joint s is the
reverse of removal. Just remember not to let the inner hub to rotate. Now
simply press the axle shaft into the new joint. Once the new joint is seated
on the shaft, install a new retaining circlip to hold it in place. Now put a
handful of grease on the CV ball bearings and the inside of the new CV
joint. Slide the CV boot over the new joint and install new clamping bands
to hold it in place. Now put a little bit of grease on the outside of the
inner CV joint, and re-install the metal cover that goes over it. Be sure to
clean off any grease on the outside of the boots and on the axle shaft.
the axles back to the car and crawl underneath. Now coat the splines of the
drive axles with oil and slide the drive flange back into the trailing arm
hub. It may take some effort to get the axle in there, but just keep at it,
and it will slide in. Install a new lock plate on the other side of the hub,
and thread the drive axle retaining nut back on, but do not tighten it just
position the inner CV joints in place and stick a screwdriver through one of
the threaded holes. This will keep the joint in place while we thread the
bolts in. But before we thread in the bolts, clean them. When I say clean I
mean remove all grease and grime. The more clean the bolts are, the less
chance there is of them loosening up over time. Once clean, put a dab of
loc-tite on the threads and thread them in. Donít forget to remove the
screwdriver as well. Now torque the bolts to 47 ft./lbs. If they are M8 size
or torque them 74 ft./lbs if they are M10 size.
put the wheels back on the car and re-install the lug bolts but do not
tighten just yet. Just get them snugged up. Now jack the car up again, and
remove the jack stands from under the car. Now lower the car, and once on
the ground, tighten the lug bolts.
last step is to tighten the drive axle retaining nuts. We have to do this on
the ground, as the amount of torque we put on this nut is enough to possibly
knock the car off the jack stands. You may even have to use an impact wrench
to get it tight. Torque this nut to 184 ft./lbs. (221 ft./lbs. on M3 models) Now put the center caps back on.
Well, there you have it - it's
really not too difficult at all. If you would like
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