Have you noticed a knocking, rumbling noise coming out of the rear of your car while going over bumps? Is the rear end sagging a little bit? Its possible that you may need to replace your rear shock mounts. A common problem on the E30 BMW 3 Series, this tech article discusses replacement of the rear shock mounts. In this article, we will focus on the E30, however the E36 and E46 BMW 3 Series Models use the same shock mount, so with the exception of a few differences, this tech article will apply to those models as well.
The first step in replacing the rear shock mounts is to remove the inner fender liners. To do this, open the trunk and look at the taillight bulb holders, notice the large round screw in the middle of each panel. Unscrew these and the two taillight panels will come off. Next, look along the upper edge of the fender liners inside the trunk, youll see a number of metal tabs holding them in place, carefully bend back these tabs, and remove the fender liners. You may have a bit of trouble removing these from out under the trunk hinges and springs, just bend the liners very carefully to get around the hinge, and remove the whole piece at one time.
With both fender liners on both sides removed, look at the shock mounts, they are located in front of the trunk lid hinges. While the car is still on the ground, its a good idea to loosen the bolts. The added weight of the car on the mount will help loosen the bolts. Loosen the two 10mm nuts on either side, but do not remove the nuts just yet.
Loosen but do not remove the lug bolts on the rear wheels. You fill find it easier to loosen the bolts with the car still on the ground
The next step is to jack up the rear of the car. A good resource for this is Waynes tech article on jacking (insert article link here) Let me take this opportunity to stress the importance of safety while jacking. Be sure to always use good quality jack stands whenever you are jacking any car. NEVER rely on only a jack to hold the car up. You can inflict serious injury to yourself and your car.
Keep in mind that this procedure is the same on both sides of the car, hence I have written out the procedure for only one side.
Once the car is jacked up, remove the rear wheels and look at the rear of the control arms where the shock absorber bolts on. In order to replace the rear shock mounts, we will need to remove the shock absorbers.
To get the shocks off, first place a floor jack under the rear control arm. This will support the rear control arm when you have the shocks removed, and prevent the control arm from swinging down and causing possible damage to suspension components.
Next, use a 19mm wrench or socket to loosen the lower shock absorber mounting bolt. Do not remove the bolt just yet, just get it loose. Next, go inside the trunk and remove the two 10mm nuts that hold the shock mount in place. Now, go back down to the lower mounting bolt and remove it, while holding onto the shock. Once you have the lower bolt removed, the shock/shock mount assembly will drop down out of the perch and free of the car. Be sure that you also remove the old gasket that seals the shock mount to the body.
Now to remove the shock mount from the shock, place the shock in a vise or secure it in some other means, and loosen the 17mm nut at the top. You will now notice that as you turn the nut, it will also turn the shock rod. If you look at the top of the shock rod, you will see a square indexing cut into it. Use a pair of vise-grips to secure this square. This will secure the shock rod, and allow you to remove the nut.
With the nut removed, simply slide the old mount off the top of the shock. Be sure to keep the large washer underneath. Now slide the new shock mount over the shock rod and place the large washer over the top of the mount and install a new 17mm locknut. Use the same procedure of holding the shock rod, while you tighten the nut. BMW recommends you torque the nut to 11ft/lbs. With the nut tightened and secured to the shock rod, place a new gasket over the top of the mount and from under the car, position it in place in the shock perch. While holding it in place, slide the lower shock-mount bolt through the shock and into the control arm, but do not tighten the nut. Now go inside the trunk, and re-install the two 10mm nuts and torque them to 17ft/lbs. Once the upper nuts are torqued, you can torque the lower mounting bolt. BMW recommends a value of between 52 and 63 ft/lbs.
With the mounts in place, and everything tight, put the wheels back on and tighten the lug bolts. Lower the car and re-tighten the lug bolts. With the car on the ground, you can now re-install the fender liners by carefully orienting them into position around the trunk lid hinges then bending back the metal tabs, which hold the liners in place. The last step is to re-install the taillight bulb holders and tighten the screw that holds them in place. Make sure that you have these holders oriented correctly, as it is possible to put them on backwards.
Now, take the car out for a spin. You should notice that the rear end of the car feels much more stable over bumps, and should be silent. After about 50 miles or so, Id re-check the nuts and bolts for tightness and re-adjust as needed.
Well, there you have it - it's really not too difficult at all. If you would like to see more technical articles like this one, please continue to support Pelican Parts with all your parts needs. If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one. Your continued support directly affects the expansion and existence of this site and technical articles like this one. As always, if you have any questions or comments about this helpful article, please drop us a line.