Help! Rear trailing arm bolt holes damaged

[trm04]

Hi all,

I am currently in the process of replacing my rear spring plates with new sway away adjustables. In the process I have found that the holes in the trailing arm appear to be flogged out. I presume this is because the bolts have been lose at some point and the movement had flogged out the holes in both the spring plates and the trailing arms. You can see that it has actually broken the top spring plate hole.

So I have new spring plates but my question is what should I now do to the trailing arm holes. The options I can think of are:

1) Leave as it, tighten with new bolts to spec and monitor it for any movement.
2) Try to repair it somehow by drilling the hole larger and pressing in a smooth bore bushing of some kind. Does anyone else have any other repair method suggestions?
3) Try to repair the hole with some kind of high strength metal epoxy, redrill the hole to the correct size and monitor for movement?
4) Replace the trailing arm. This seems like a big job which I would like to avoid if possible.

Appreciate your thoughts and suggestions on what to do next?

[SCadaddle]

I wouldn't go with Option 1.
Options 2 and 3 would require removing it, fixing it and reinstalling it, correct? If so...
By now you are 1/2 the way into Option 4. Find a replacement and finish Option 4.

You asked, that's my opinion.

[Dpmulvan]

What year is your car? I might have a spare set. Either remove it take it to a job shop have them weld and tap it or replace it. Epoxy on a suspension I doubt would hold, probably not safe either.

[HaroldMHedge]

Another option would be removing the arm have the holes welded up then redrill the holes. The machine shop labor would most likely be high enough that it would be cheaper to find a good used trailing arm and replace it. (Edit: Dpmulvan beat me to the welding.)

I agree with SCadaddle, go with Option 4.

[Walt Fricke]

While your picture makes it clear that the spring plates are not worth fixing (though they could be welded and redrilled, but why), they don't show as clearly just how much damage the loose bolts caused to the holes in the aluminum trailing arm.

The holes aren't what keeps the spring plate in position with the trailing arm. It is the stretch of the bolts (aka, torque) which clamps the two together. The big washers spread this clamping force around on the aluminum. Some ovality ought not to matter here, though it might make the alignment shop's job a bit harder. But none of these are a press fit or anything like that.

If this isn't appealing, you ought to be able to bush the holes easily enough. Drill the holes out with a hand held drill to a pre-determined ID. I don't see why you would need to remove the arms to do this. Get some tubing which is a snug fit for the bolt, but has a wall thickness wide enough for the purpose. If you can swing it, you could even do this so you could shrink fit the bushing in place - bushing in your freezer, banana arm area heated with a propane torch, quickly press the cold bushing in. But an easy press fit with a C clamp should work.

You could have a machine shop make the two bushings for you if you can't find tubing or bushings at your nearest hardware store.

Must have been some ugly tire wear back there for a while!

[gtc]

Replace the trailing arm with a good used unit.
Probably easier than trying to have yours repaired, and shouldn't be too expensive.

[Walt Fricke]

Before deciding to replace the trailing arm, I'd read the recent posts here from guys doing that and confronting a variety of obstacles. Technically it is pretty straight forward, but as a practical matter, by someone with modest experience and tools, on jack stands in a residential garage, who has never done it, it is not a trivial task.

You have to remove the axle, disconnect the brake lines and remove the brakes, and press in a new bearing in the replacement part, on top of dealing with the nut and bolt where the arm attaches to the torsion tube.

You could take the replacement arm and bearing to a shop and have them press the bearing in - that would cut down on one tricky part.

[Knockdown]

If you can set and check the alignment yourself, which is fairly easy with strings and a digital level, I would try #1 first. Who knows, maybe you can get a little extra camber. .

[1ricardo]

IMHO, the #4 option is the only option....

[Evans, Marv]

^^^^^^ This. Bite the bullet and do it right. After it's done, you'll never have to do it again as opposed to your other options.

[1979-930]

With shop labor rates what they are today I think bushings or welding will cost about the same as a used one.
And is the repair going to be exact? What if the guy boogers up the location of one of the holes.
Then you have a bunch of wasted time and money. Not worth the risk.

[jjeffries]

Where does OP live? It's possible someone/one of us would help him. John

[trm04]

Thanks for all of the feedback. To answer the questions raised:

The car is a 1986.

In terms of the damage to the trailing arm, it looks to have elongated the holes downwards by approximately 1/4 inch.

Funnily enough I have driven the car like this since I bought it a year ago and have done approximately 3000 miles without any noticeable problem. In terms of the tire wear, the tires have been on the car for the last 12,000 miles and look perfect. Very little wear and it is even.

Seems like most people are are leaning towards option 4. To be honest I was leaning towards option one but am now reconsidering. I will do some more reading into how difficult it is to replace the trailing arm. Finding a second hand one may also be a challenge as I am located in Sydney Australia.

If I take the arm off I will be replacing it due to how much work it takes to get to that point. I won't repair it is it comes off. My only consideration was to repair it in situ and see how it goes. I was initially thinking along the same lines as Walt as in drill it out and press in a suitable bush with a C clamp.

Thanks for all the feedback. I have been pondering this for a week or so and thought here would be a great place to seek some input.

[ClickClickBoom]

If you are removing and replacing the parts already, you spent a pile of cash on new stuff already.
While I am an advocate of fixing stuff, by the time you remove the arm, set it up in a mill to determine the proper hole distancing. Hand drilling is not precise enough or you will be back in the same place. Your costs are spiraling out of control. Then you have to find out what grade aluminum the base material is made out of. Welding a chunk of aluminum that big preheating will be likely. Knowing the wall thickness will tell. Use the wrong rod and you will be chasing cracks, or not weld at all.
But what do I know, 35 years Aircraft & Powerplant mechanic, welder for 40 years certified 6G in TIG. My home shop has a milling machine, lathe and a whole lot of fabrication tools.
If you brought it into my shop I would tell you to go to Parts Heavens website and order a good used part, way cheaper and the peace of mind will go a long ways.
Some things are just easier to replace. If you search my posts, you will see that I am not shy about tearing into stuff, but I give suspension the respect it deserves, there is a lot of spring tension involved.
If you cant find a good replacement Down Unda, PM me and I will source one for you and ship it. No mark-up, actual cost.

Here:
https://www.ebay.com/itm/Porsche-911-OEM-Trailing-Arm-Right-9113315140R-3/263469747611?epid=1373033754&hash=item3d58054d9b:g:IvUAAOSw~o5acmwF

https://www.ebay.com/itm/Porsche-911-OEM-Trailing-Arm-Left-9113315130R-4/253400902705?epid=1871418832&hash=item3affdeec31:g:sAIAAOSwJ71acmym

[porsche930dude]

I dont think id want to drill it out for bushings. To do that on the car and get them in the right place would be pretty difficult. I suppose you could use some sort of drill guide. I wouldnt like to do #1 either but #3 seems like a good option. That will keep the bolt where it belongs. It really shouldnt loosen up and cause any future problems. Another thing to consider is the condition of the trailing arm bushings. It may be time to replace those anyway.

[gomezoneill]

Originally Posted by ClickClickBoom

If you are removing and replacing the parts already, you spent a pile of cash on new stuff already.
While I am an advocate of fixing stuff, by the time you remove the arm, set it up in a mill to determine the proper hole distancing. Hand drilling is not precise enough or you will be back in the same place. Your costs are spiraling out of control. Then you have to find out what grade aluminum the base material is made out of. Welding a chunk of aluminum that big preheating will be likely. Knowing the wall thickness will tell. Use the wrong rod and you will be chasing cracks, or not weld at all.
But what do I know, 35 years Aircraft & Powerplant mechanic, welder for 40 years certified 6G in TIG. My home shop has a milling machine, lathe and a whole lot of fabrication tools.
If you brought it into my shop I would tell you to go to Parts Heavens website and order a good used part, way cheaper and the peace of mind will go a long ways.
Some things are just easier to replace. If you search my posts, you will see that I am not shy about tearing into stuff, but I give suspension the respect it deserves, there is a lot of spring tension involved.
If you cant find a good replacement Down Unda, PM me and I will source one for you and ship it. No mark-up, actual cost.

Here:
https://www.ebay.com/itm/Porsche-911-OEM-Trailing-Arm-Right-9113315140R-3/263469747611?epid=1373033754&hash=item3d58054d9b:g:IvUAAOSw~o5acmwF

https://www.ebay.com/itm/Porsche-911-OEM-Trailing-Arm-Left-9113315130R-4/253400902705?epid=1871418832&hash=item3affdeec31:g:sAIAAOSwJ71acmym

This ^^^^ cant go wrong here. That's a lucky break if I ever saw one.

[gtc]

With the spring plates removed the trailing arms are basically halfway out already. Might as well take the opportunity to pull them both off the car and check out the bushings, bearings, and CV joints while everything is reasonably accessible.

[Evans, Marv]

Yep. You can pick up good used swing arms and spring plates very reasonably, and the bushings, bearings, etc., etc. aren't expensive. It's actually not hard to do and will last as long as you have the car. Plus, when you go to sell it, that will be a plus for the car. One reason I like my car is that I have learned a lot working on it (brakes, suspension, electrical, windows, and on and on) , and they aren't so complicated we all can't work on them.

[ClickClickBoom]

Originally Posted by Evans, Marv

Yep. You can pick up good used swing arms and spring plates very reasonably, and the bushings, bearings, etc., etc. aren't expensive. It's actually not hard to do and will last as long as you have the car. Plus, when you go to sell it, that will be a plus for the car. One reason I like my car is that I have learned a lot working on it (brakes, suspension, electrical, windows, and on and on) , and they aren't so complicated we all can't work on them.

Add some monoballs, you would be 1/2 way there anyways!

[trm04]

Ok. Sounds like we are replacing the trailing arm.

So what do I need:

1) Second hand left rear trailing arm
2) Some new trailing arm bushes - suggestions? I looked up monoballs as suggested but seems a bit overkill if the rest of my suspension is basically all standard.
3) Do I need these ezy pins to enable me to get the bolts in without removing the transmission? From what I have read it seems to indicate this. https://www.wevo.com/Products/SuspensionProducts/WevoSuspensionProducts-EZPins.htm

I have records that the right wheel bearing has been done but never the left. So should I do that while Im in there?

Man this thing has really spiraled since my initial intent of putting some sway away spring plates and bushes in. Haha