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Trailing Arm bushing replacement

I'm going to have the engine and transmission out of my car soon for some servicing. I thought it might be a good time to replace the trailing arm bushings with OEM. My question..can I do this without removing the banana arms? I'm trying to avoid the suspension slippery slope at this time and would rather not have to cough up the additional cash for an alignment which I'm assuming would need to be done if the trailing arms where removed.
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Old 02-24-2007, 10:50 AM
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Although it's easier to do this on the bench, it can be done with the arms in the car. Having the engine/trans out makes it a lot easier.

The difficult part is removing the outer metal shell of the bushing from the arm. The trick to doing this on the car is to slice the shell with a hacksaw, being VERY carefull to not nick the AL traliing arm. You don't even need to cut all the way through the metal, just close. This will releive the tension of the press-fit and allow you to tap it out.
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Old 02-24-2007, 12:00 PM
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Ron:
There was a thread just recently about someone fighting with these.
Why do you think the bushings need replacing?
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Old 02-24-2007, 12:18 PM
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Thanks Chuck, I figured I could do this on the cheap and it would be one less task to attend to when I do the suspension in the fall.
Gunter...I feel that the 30 year old rubber is ready for replacement...and since the engine and tranny will be out the way now would be the time to do it. Yes, I suffer from 'while your in there'!
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Old 02-24-2007, 07:48 PM
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Well, it's your time. The rubber is not that thick (nothing like the torsion bar bushings), and it is captive between two steel pieces. I took mine out last spring, and the rubber seemed fine. Of course I did not do an engineering analysis on its properties after 30 years. The removal was to change to a spherical bearing. I don't think I'd have done it otherwise.

I don't think you need to remove the pesky outer stamped and formed thinnish steel shell (a pain), as it is not a wear item. That has to come out when installing spherical bearings.

The machined inner steel piece and the rubber came out easily enough on mine. If you are replacing the rubber, I'd leave the outer shell alone. But maybe these come as a full assembly with the outer steel piece attached or bonded or something already to the rubber?

This "bushing" is the same from '74-'89, and from the parts diagram it sort of looks like what you get is the central machined steel piece and the rubber and maybe the spacer washers. The outer pressed in insert may simply be a part of the trailing arm and not separately available.

You'll know when the parts you order arrive.

Walt
Old 02-24-2007, 10:52 PM
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Quote:
Originally posted by Walt Fricke
The machined inner steel piece and the rubber came out easily enough on mine. If you are replacing the rubber, I'd leave the outer shell alone. But maybe these come as a full assembly with the outer steel piece attached or bonded or something already to the rubber?
Walt's suspicions are correct.

They do come as an assembly, and you do not want to take the rubber out of the metal cylinder (shell) on the new bits. You will never get them back together. Take the old metal cylinder (shell) out of the arm and press the new one in as an assembly.
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Old 02-24-2007, 11:06 PM
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I ordered a set of four from Pelican a few weeks ago anticipating the engine drop. I spent some quality time examining these expensive little parts and realized right away that removing the outer sleave from the assembly was a bad idea. My plan is to punch out the old from one side and then maybe use a section of pipe or a socket to drive out the other. Then as Chuck suggested hacksaw the thin sleave or use a dremel to grind a valley in the sleave. I'm thinking I can press the new guys into place with a C-clamp, some heat on the arm or a BFH. I just wanted to make sure that the arms will drop down enough to allow me to attempt this procedure and not find myself forced to remove them and need an alignment.
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Old 02-25-2007, 07:04 AM
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I did this many years ago, and it was a pain. These days I have a home alignment system so I removed the trailing arm entirely when I recently replaced the monoballs.

What I'd like to hear is how others were able to get the trailing arm out of the chassis mount with the spring plate is still hooked up to the torsion bar.

When I did mine I jacked up the spring plate, compressing the torsion bar, and bent the spring plate sideways...I'd never do that again.
Old 02-25-2007, 07:44 AM
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Ron:
Some lube might help.
Vaseline doesn't attack rubber.
What are you doing to the engine/transmission?
Check and paint the tin ware if needed.
If you do the clutch, check the guide tube for wear.
My 3.0 is out on the floor and the 3.2 is ready to go in but, since it is still below 0, I am waiting for just a little warmer temp.
JW rebuild my 915.
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Old 02-25-2007, 07:48 AM
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I just put monoballs in my car this month. I recommend you put the new rubber bushings in a drawer and don't look at them again. If you try to take the bushings out while the arms are still in the car I think you'll hate yourself after about 4 hours of frustration.

The old bushings were hard to take out and I had the arms out so I could work on them. Pressing the new arms in will take some heat in the aluminum and alot of pounding if you don't have a press.

Finally the old bushings were in great shape. They are actually quite thin and don't seem to get sloppy.

-Andy
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Old 02-25-2007, 09:01 AM
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You will need to disconnect the spring plate from the trailing arm to allow enough movement to get the job done.

I would be careful with heat. The new rubber won't like this.

To install the new ones, fashion a tool/press out of a long fully-threaded bolt, a couple washers, and nut. Put the bolt through the bushing and trailing arm, then crank it down to draw the bushing in.

The key to removal is cutting as I mentioned above.
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Old 02-25-2007, 09:13 AM
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Quote:
Originally posted by Chuck Moreland
You will need to disconnect the spring plate from the trailing arm to allow enough movement to get the job done.
Now it makes more sense.
But, disconnecting means disturbing the eccentric bolts for camber and toe in effect changing the alignment.
I read that Ron didn't want to do that.
Can he mark the position of the spring plates, and eccentric bolts, accurately to keep the alignment?
Sounds like a tight job.
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Old 02-25-2007, 09:44 AM
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I posted a thread a long time ago about changing bushings without removing from the car. Click HERE
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Old 02-25-2007, 09:48 AM
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Quote:
Originally posted by Gunter
Now it makes more sense.
But, disconnecting means disturbing the eccentric bolts for camber and toe in effect changing the alignment.
I read that Ron didn't want to do that.
Can he mark the position of the spring plates, and eccentric bolts, accurately to keep the alignment?
Sounds like a tight job.
The car will require alignment after this job is done. Marking the position is okay as an approximation, good enough to drive to the alingment shop.
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Old 02-25-2007, 11:35 AM
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There seems to be a belief that you do not necessarily need to replace the trailing arm busings just because the car is old. I am planning my suspension upgrades and was considering upgrading the stock 1981 bushings to polygraphite with Neatrix spring plate bushings. Are you all saying that I might not need to replace the trailing arm bushings? How would I know one way or the other? Lastly, what is this metal outer shell that you are cutting? I look the diagrams and neither the rubber or PG bushings show an outer metal sleeve. I am probably missing the obvious here.

This probably warrants its own thread, but will I really notice an increase in handling by going to 22/28 torsion bars and bilstein sports? I am planning to auto-cross and maybe a DE or two. Suspension is original except for newer Boge struts. The bushings need replacing and I want to do it all at once, but like has been said... very slippery slope.
Old 02-25-2007, 12:05 PM
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Munsonbw..I know for a fact you don't want to replace the rubber monoballs with Polygraphite...I'm sure others will jump in.

Back to my little project. With the drivetrain out of the car I will have easy access to the bolts. My plan was to remove those and thought the end of the banana arm would be free to drop down a few inches. I figured I could also remove the lower shock bolt and perhaps the lower springplate stop bolt if I needed to. I would be supporting the banana arm with a jack.
Foolishly I thought that the difficult part was going to be removal of the bolts [soI bought a pair of new ones in the event I need to cut the old ones out. After that I figured my next test would be the removal of the old bushings.. which at this point I feel I understand the concept and while it might be a pain, seems doable.
My confusion remains because I'm not sure if the arms will drop free of the brackets and allow me to do the R&R without disturbing the alignment.
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Old 02-25-2007, 12:52 PM
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Muns - Ron speaks the truth.

Most aftermarket stuff is useful, and some is an improvement over the factory (at least for altering the comfort/performance balance toward performance). So polyurethane trailing arm inner bushings are an exception -- a part you don't want to use.

The spring plate bushings, and their counterparts up front on the A arm, are dealing with rotation pretty much around a fixed axis. So they can be replaced by a more rigid material without affecting their ability to handle the motions required. You could use bronze bushings or needle bearings (I've got both in my SC), or urethane (which I used to have) or Delrin.

Not so this inner banana arm bushing. Think about what happens when you adjust toe (easier to visualize than camber): you are moving the outer end of the banana where the wheel and axle are forward or backward to get the tire to point where you want it. So it has to be able to move in a horizontal arc, whose center is the inner mount.

Now think about what is going on at the inner mount: If that bushing were totally rigid you could not move the trailing arm forward or back at all (short of flexing the aluminum). A rigid bushing allows pivoting only around one axis, and the big bolt in there is horizontal, allowing for the up and down suspension motion. To adjust toe you need movement around a vertical axis. Polyurethane is not totally rigid, but it is pretty close so you are inducing a bind. Suspensions work best when there is zero friction in their movement. The rubber works fine because it is compliant (it squishes as needed).

If you've already bought urethane bushings for this location, do what I did with mine when I started to understand all this: put them in the junk box, vowing to find some other use for them some day repairing your garage door or something.

Walt Fricke
Old 02-25-2007, 03:19 PM
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Ron

Your plan for removal of the pesky inner steel sleeve is what mine was. I couldn't get it to work. There is no place to get a purchase inside to drive bushing #1 out. They are thin to begin with, and nearly mate in the middle. Once you do get one out, driving the other one out is a piece of cake. And after learning on one arm, the other arm should go much faster.

Hence the expedients. Paul S must be an artist with a cutting torch, as I can't imagine how he could cut any part of this shell without damage to the aluminum immediately below it. Especially working under the car. So that's not for me - I've got to live within my skills, such as they are. I seldom use my torch, and don't have any sort of cutting tip small enough.

Chuck says cut with a hacksaw. If you have things in a vice on the bench this sounds good - thread the blade through the hole, reattach to handle, use some muscle. Pretty tough if you are doing any of this under the car. I tried cutting the lip surface, and maybe a Dremel cutoff wheel would have done good work so you could raise a flap.

When I inquired about techniques someone suggested careful bashing, which naturally appealed though it was made more difficult by the fact that the arm, under the car, is not rigid at this point, so bashing loses some of its effectiveness.

For me the trick was using a small chisel to tease up a lip a bit. At that point I could drive a long punch in and right through the metal, creasing it inward nicely in the process. And use this to pry. Were I to do this again in the car I think I'd try the Dremel route preparatory to the punch.

Walt
Old 02-25-2007, 03:46 PM
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Thanks Walt I will keep you all posted on how this turns out.
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Old 02-25-2007, 06:29 PM
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Porsche Crest Bushing picture

For those wondering what this bushing business is about, here is a picture of one trailing arm's worth of used rubber bushing components. The thin steel piece is a press fit into the hole in the end of the aluminum banana arm. The rubber fits into that, and the stout inner piece goes inside the rubber. As a replacement, all three are, we learned, already assembled as a unit. So some lubricant around the outside of the steel shell (or in the hole in the arm) to ease assembly can't harm the rubber.

The separate pivot bolt runs through the center of it all.

The auto focus didn't work as well as it sometimes does. These 30 year old rubber pieces are still supple, and most of the more obvious damage to them was done during extraction.

My take: for a street only car, leave them alone unless you can move the inner end of the banana around by hand when the pressure is off of it or have other evidence that they have failed.

Of course, if you have a set in hand, have some time, and enjoy a challenge, there is no downside to new bushings in this location.



Walt
Old 02-26-2007, 11:07 AM
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