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Pelican Technical Article:

BMW E30 3 Series Trailing Arm Bushing Replacement
Jared Fenton
Wayne R. Dempsey

Difficulty Level: 3
Difficulty scale: Adding air to your tires is level one
Rebuilding a BMW Motor is level ten

     In this continuing article on rebuilding your E30ís suspension, we will focus on replacing the rear trailing arm bushings on my 325is. This is a more complex job for the amateur mechanic, but as with all things, with the right tools and information, you can do the job yourself. Keep in mind that this article applies to all E30 models, however the early 318i models from 1984-86 use rear drum brakes rather than discs. This article also applies to the E36 318ti models from 1995-99. In order to keep costs down, BMW used the same rear suspension from the E30 on the 318ti.

     These tech articles are written with the home mechanic in mind. For the most part, these articles require nothing more than a decent set of tools, including a good metric socket set and ratchet. It is also well worth the money to invest in the following tools. First, a good quality vernier click style torque wrench. You will need this in order to make crucial tightening torques when working on suspension bolts and nuts that are under extreme loads. Next and most crucial, a good set of jack stands. Try to get some high quality ones that have a sturdy construction and donít look too flimsy. Usually you can get a set for around

     Why replace the trailing arm bushings? Over time, these small bushings get subjected to a lot of wear. They are the primary support point for the suspension pivot. Many times a worn out bushing will give your car unpredictable handling characteristics, as well as an incorrect rear wheel camber. Just remember, rubber dries out over time and can start to crack. Often this is what causes these bushings to wear out.

     To replace the bushings, we will need to remove the trailing arms from the car. In order to that we must also 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. No w we will need to loosen this nut. Loosen the 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.

     Now, letís jack the car up. First, chock the front wheels to keep them from rolling while you have the rear wheel 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 enforced 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 floor boards. A handy reference is Wayneís article on jacking up your BMW.

http://www.pelicanparts.com/bmw/techarticles/E36-Jacking_Up/E36-Jacking_Up.htm

     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 Allen 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.

     Next, use an Allen head socket and remove the 6 bolts on each side. The drive shafts will now be free of the differential. Use some wire or rope to hold the shafts up; otherwise they will just hang down free and put stress on the CV joints.

     Go back to the brake rotors, and remove the driveshaft retaining nuts and the lock plates underneath. Now, bolt a puller to the rotor face using the lug bolts to hold it on. Now use the puller to push the driveshaft flange out of the rotor/hub on each side. Have a helper hold the drive shafts when you do this. Keep pushing with the puller and the driveshaft will pop out. Now remove the wire supporting the shafts and set them aside.

     Now is a good time to inspect the rubber CV boots. These boots are used to hold grease, keeping the CV joints lubricated. If there are any tears or cracks in the CV boots, replace them.

     With the drive axles now removed, now we can focus on the steps involved to remove the rear trailing arm. First, Look the rear brake calipers. Disconnect the brake wear indicator sensor on the passenger side and also the ABS speed sensor connections. Now find the brake hose and trace it back to itís connector on the trailing arm. Because of the way the hose fits into the mounting bracket, we will need to disconnect the brake lines. First, open the hood, take off the brake reservoir cap and place a small piece of cellophane over the top. Now put the cap back on. This has the same effect as putting a straw into a glass of milk, then putting your finger over the top and lifting the straw out. The milk stays in the straw. When we disconnect the brake lines, the cellophane will help keep the brake fluid in the lines, and not spilling all over the floor. Undo the fittings on the trailing arm and plug the brake line to keep fluid from spilling out all over the place. Now look under the control arm and locate the two 13mm nuts that secure the sway bar end links to the trailing arms. Just remove the nuts. As you lower the trailing arm they will automatically withdraw from the arm.

     Now, place a jack under the trailing arm assembly to support it. Loosen and remove the lower shock absorber mounting bolt on both sides. Now, slowly lower the jack. The sway bar end links should automatically withdraw from the trailing arm. Now have a helper stand on the trailing arm to further lower its angle. Now remove the coil spring from the car. By lowering the trailing arm, we are now able to access the trailing arm mounting bolts in the front. Remove these bolts and remove the trailing arms from the car. You may need a helper to support the rear of the trailing arms while removing.

     Now you will need to take the trailing arms to a competent machine shop to have the old bushings pressed out, and have the new ones pressed in. This should not be more than $30 at any shop. You can press the bushings out yourself, however without use of a hydraulic press, you may find this difficult.

     Once the bushings are in, get the trailing arms lined up to the brackets on the rear axle carrier, and have a helper hold it in place. Now slide the mounting bolts back in place and torque them to 30ft./lbs. Now, place the coil springs back in the car, making sure the rubber retaining pads are lined up correctly. Now, rotate the control arms upward, making sure that the sway bar end links slide into the mounting holes while the arms move up. Now use a jack to support the trailing arms and re-install the lower shock absorber mounting bolts. Torque them to 60 ft./lbs. Now, put new self-locking nuts on the bottom of the sway bar end links and torque to 17 ft./lbs. Now reconnect the brake line fittings. Reconnect the brake wear indicator and ABS speed sensor connectors at this time as well.

     Now lube the outside shaft of the driveshaft and push them back into the trailing arm hub. Clean the threads of the flange really good and oil the threads. Now slide the new lock plate on and thread the retaining nut on finger tight. Now re-install the 6 Allen head bolts that hold the drive axles to the differential. Make sure these bolts are clean before re-installing and use a small dab of Loc-tite on the threads. This will help to keep the bolts from backing out. Now use a criss cross pattern and torque each bolt incrementally first to 20 ft/lbs, then one more time to 46 ft./lbs.

     Now we are ready to bleed the calipers. In this instance, we will assume that you have a helper to do this. First, loosen the bleeder screw on the caliper, then quickly snug it back up, we want to just get it loose, not remove it. Next, get a jar and fill it about halfway with fresh brake fluid. Place one end of a clear plastic hose over the bleeder screw and run the other end into the jar.

     Next, open the reservoir cap, remove the cellophane and check the fluid level. Top it up as needed. Leave the cap off, as this will help to draw fluid through the system. Have your helper pump the brakes until pressure begins to build up. Then have your helper step on the brakes to hold the pressure and open the bleeder valve for about 1 second then quickly close again. You will see fluid flow through the hose with a lot of air bubbles in it. Having the hose in a jar of brake fluid prevents air from flowing back into the caliper.

     Again, have the helper again build up pressure on the brakes and hold the pedal down. Open the bleeder valve for about 1 second then quickly close. You will want to repeat this step until there are no more bubbles flowing through the line.  As the air is bled from the lines, it will take less time for the brakes to build up pressure. Check the fluid level in the reservoir while your helper is pumping the brakes to build up pressure. Do not let the reservoir run dry or you will have to bleed all over again.

     Once the lines are bled, clean up the area around the caliper. Use the brake cleaner to get rid of any extra fluid around the area. Once clean, remount the wheels, install the lug bolts snugly, but do not tighten yet. Now jack the rear of the car up again and remove the jack stand. Now lower the car. Be sure to do this one side at a time. Now simply tighten the lug bolts in a criss-cross pattern.

     Now we need to torque the drive flange retaining nuts. Having the wheels on the ground will help you torque the nuts down. With the car in the air, you risk knocking the car off the jack stands. We are going to torque these nuts to 150 ft./lbs. Thatís a lot of torque! You may need an impact wrench to get it there. Once torqued, just re-install the center caps and take the car for a spin around the block. You should notice a stiffer feel from the rear. And the handling should be tight and responsive.

     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.

Comments and Suggestions:
Videoman Comments: Just curious-what size it the axel retaining nut?
I know I could check. it's that simple, but if you know then I won't have to wonder if I have a large enough one or nut. It sounds like this is an all day job, and your article is very well written. thanks, Ed
October 8, 2012
  Followup from the Pelican Staff: The sizes vary from the year and aftermarket kits sometimes changes the size with the new axle nut. They could be 27, 28, 30 or 32mm. - Nick at Pelican Parts  
Yib Comments: Figured it out. Lowering the subframe/carrier axle just a couple of inches on the side I'm working on was easy and did the trick. Wish I hadn't removed the fuel tank hose. Wasn't necessary.
June 6, 2012
  Followup from the Pelican Staff: Thanks for the tips for our readers - Kerry at Pelican Parts  
Yib Comments: The inner race of an old, shot rear wheel bearing is stuck in the trailing arm bearing housing, and after every attempt to press or bang them out has been frustrated, I finally decided to remove the trailing arm completely and take it to a machine shop.

Other than the mounting bolts being in a very tight location for a ratchet, I managed to get almost completely through the time consuming task. Completely lowered, the coil spring isn't under much tension and doesn't need to be compressed. The hardest part was just prying it off the lower mount.

But here's the frustration kicker: the outboard trailing arm mounting bolt doesn't clear the inlet tube to the fuel tank. I thought it was just the hose that was in the way, but after pulling the hose off, there's still the metal nipple block full travel of the bolt. I don't see how to remove it without attacking the inlet which I don't want to do, and certainly not with a cutter or lowering the subframe an inch or two.

Am I the only one with an E30 that has the fuel tank interfering with the trailing arm bolt? I haven't seen any mention of this anywhere.
June 5, 2012
  Followup from the Pelican Staff: No, dropping the subframe is the common work-around. On many German cars the nuts and bolts are not always easy to access. - Kerry at Pelican Parts  
Joseph Comments: Jared,
Fantastic write-up, but I was hoping to find some information in regards to the coil springs. This will be my first time swapping my trailing arm bushings and just looking at them, I really feel as if i should compress the coils first before removing any bolts from the trailing arms. Correct me if I'm wrong, but aren't those arms under some serious down force from the springs? Thanks a million.
May 31, 2012
  Followup from the Pelican Staff: No there is not much tension with the car in the air and the suspension suspended. Remove the outside trailing arm bolt first. If you are still concerned put a long metal bar up through the middle of the spring and that should hold it captive - Kerry at Pelican Parts  

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