Aaron K limitedslip.net

2Jul/130

trailing arm bushing hell

I know bushing jobs can be a huge pain, but the rear trailing arm bushings on the e24/e28 chassis take the cake. e30 trailing arms were a walk in the park, they were just rubber and could easily be removed. Not so with the e24/e28...

I started this mess by first trying to fit the control arm into the press, when I realized (like others) that the big C channel supports for the arbor plates from the harbor freight press wouldn't let you get the trailing arm in the right position. I've seen pictures of some people cutting the notch out, but I didn't want to weaking the existing one any, so I picked up a bit of 3" x 1/4" plate, some angle iron, and made a new one that should be strong enough but wouldn't have the same clearance issues. Here it is next to the stock one:

IMG_0166

 

The design seemed to hold the 12 tons without any issue. The vertical plates didn't separate or bend at all. Turns out though this was the wrong solution to the problem. The trailing arm bushing wall was only about 3/16" of an inch thick. It was very difficult to get it supported on the arbor plates and still allow the pushing to be pressed through. The cutouts in the plates were all either the wrong shape or the wrong dimension. Here is my first contribution to anyway dealing with these cars using the common 12 ton harbor freight press. Don't bother making a new press support like I did. Buy these two parts from home depot:

  • 2" threaded pipe coupling
  • 2" to 1 1/2" bushing

These are the parts:

IMG_0183

And they should thread together. Cut/grind out the inside threads a bit, and the new subframe bushing should slide through nicely:


IMG_0188

 

The quickest way to remove the inside threads is a die grinder and a carbide cutting bit. Just eats through it. Now, there is a perfectly sized support for the trailing arm, a space for the bushing to be pressed through, and, now enough clearance to get the trailing arm into the press!

IMG_0186

I was using the press ram to hold it together while I took this picture. If you try to press it out like that, your trailing arm and press will become one part and you'll have a whole new problem on your hands. I used a section of pipe that fit the bushing (also from home depot), but I'm not sure that was the best. The metal was pretty soft and I had to keep cutting off the damaged end.

IMG_0243Finally I was thinking to myself, time to press these suckers out.

Well, 12 tons wasn't enough, they were thoroughly wedged in there. I'll jump a head here a bit and explain why they don't come out with that much force.

In my case at least, the bushings have an outside lip on them that you can only see if carefully destroy it. Notice how they are flared out?

IMG_0246_cropped

They appear to be designed to go in one way, and back out the same way. This is a problem with a press because you can't turn the trailing arm upside down to remove them - the other end interferes with the jack. I think this explains why so many people can't seem to press them out. The new Meyele bushings don't have any lip.

I developed a technique (by the 4th bushing, of course) that I think will help others. It is commonly known that aside from pressing, the best way to get bushing out is to cut them out. But you can't just take a sazall to them and hope they'll pop out and not destroy the housing in the process.

Here is what I think works well:

  1. Get the above press setup and the plumbing support parts. They will be necessary to position the trailing arm on the press for reinstallation.
  2. To remove them, first remove the inner portions of the bushing. Burn them out if you have to. I've heard of a hole saw being used, tried that, but the saw just got jammed in the rubber. I was able to use my press to tear out the inner bushing - the rubber didn't stand up to 12 tons at all.
  3. Once the inner part is out, you have to remove the metal shell. Get out the sawzall or hacksaw. Make two slits in the bushing about 1/4" apart. I used the sawzall for most of it, then switched to the hack say to make sure I didn't go all the way through the bushing. Get as close as possible, but don't go all the way through unless you want to damage the housing.
  4. Use a metal punch (not a chisel), to bend this 1/4" piece inward. Since you've cut through the shell most of the way, this should be fairly easy. Once you get it about half way down, the whole sleeve should just pop out.

Took me about 15 minutes to do the last bushing from start to finish. Here is what the bushing sleeve will look like when it comes out. The metal punch easily tears and rolls the leave down without a single cut mark on the trailing arm surfaces.

IMG_0255_cropped

The replacements pushed it pretty easily. Note the orientation, one end of the inner bushing sleeve is longer than the other end. The long ends should point outward. Correction: I messed up the orientation, the long parts should point inward, as shown in the diagram at the end of this post.

IMG_0261_cropped

Lets hope the fronts aren't this big of a pain.

 

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