Repair Trailing Arm? - PeachParts Mercedes-Benz Forum

Graham · #1 08-29-2013, 10:28 PM

I was about to paint trailing arms on my 85 300D, but after scraping off dirt etc, noticed some pinholes. Looks like I have some rust. Tapping indicates arm is generally solid except in those areas.

Ideas that come to mind:
-POR/JBWeld plus spray interior with Fluid Film or similar.
- Weld repair
- Replace with good used.

I am about $2600 and 9 months into an overall rust repair. But, we don't NEED this car, so there has to be a limit.

What do you think about the repair options?

cooljjay · #2 08-29-2013, 10:42 PM

I would replace it with a good used one....mainly because the shock mounting studs look bad, I don't know if that nut would ever come off when it was time to change the shock....plus I wonder what it looks like under the spring shim....I would hate to go over a speed bump and have it crack or the spring pop out....I suppose the only to true way to fix it and see how bad it is, is to remove it off the car....

Diesel911 · #3 08-29-2013, 10:57 PM

It looks like there is a crack on one side where the Shock is.
If those are Nuts and Bolts that are mounting the Shock you could make and insert from one or 2 Washers; on washer on each side with the Holes for the Bolts and JB Weld it in place and use longer Bolts.

The Metal on the Arms is thin. I have never used a MIG Welder so I don't know if it can be done with that.

In the Olden Days shops did not have a MIG Welder but the did have a Torch. I believe the Pin Holes could be Brazed over.

You could use some Fiber Glass Cloth and JB Weld Epoxy to cover over the Pin Holes.

charmalu · #4 08-29-2013, 11:46 PM

That trailing arm is 2 pieces of sheet metal that is stamped out and welded together along the flange area. If you see pin holes now, that is only the tip of the ice burg.

I would replace the Trailing Arm with a good used one. clean it up, and POR it with several coats of paint.

There has been several threads where these things have cracked and also the shock fall out where it is bolted in. This is a safety issue for sure.

Rust battle #434 Rear Control Arm

IT FELL OFF! :)

rear trailing arm broke

rear trailing arm broke

Benzworld.org - Mercedes-Benz Discussion Forum - View Single Post - rear trailing arms 84 300d

Charlie

Stretch · #5 08-30-2013, 03:01 AM

I think good used / new (with serious discount!) is the best option.

Graham · #6 08-30-2013, 09:49 AM

I realize that new or good used is the best option. But at 73, I am afraid the replacement job is beyond me. If I found good used trailing arms, what would shop time be? If subframe was removed, new mounts plus the trailing arm bushings would be needed. The rubber boots on the side shafts also look like they should be replaced soon.

My concern is that all this done by a shop might cost me more than a new car

Alternative is to patch as best as I can. Welding on a reinforcing plate, might be a stopgap measure, but to do that properly, presumably shock should come out and perhaps spring too?

Assuming I keep car and drive it as is, it will only be used as an around town car to get me to places like golf course or marina and shops. It would save me using my 72 350SL. For that, I will have to review just how bad the rust is. Maybe drill a few tiny holes. I wish I had a wall thickness meter like we had when I was working!

Stretch · #7 08-30-2013, 10:15 AM

Quote:

Originally Posted by Graham

I realize that new or good used is the best option. But at 73, I am afraid the replacement job is beyond me. If I found good used trailing arms, what would shop time be? If subframe was removed, new mounts plus the trailing arm bushings would be needed. The rubber boots on the side shafts also look like they should be replaced soon.

My concern is that all this done by a shop might cost me more than a new car

Alternative is to patch as best as I can. Welding on a reinforcing plate, might be a stopgap measure, but to do that properly, presumably shock should come out and perhaps spring too?

Assuming I keep car and drive it as is, it will only be used as an around town car to get me to places like golf course or marina and shops. It would save me using my 72 350SL. For that, I will have to review just how bad the rust is. Maybe drill a few tiny holes. I wish I had a wall thickness meter like we had when I was working!

Oh come on - don't pull the I'm 73 card on us! You're more active than most of us here.

I know the replacement seems like a big job - and it is - but with help you could easily do it in a weekend. I can post a link showing how to do the job if you want. The best trick is to undo all the bolts and bits and then "just" lift the back end of the car and roll the whole subframe out from underneath with the wheels still on it. If you can think of a way of doing that with relative ease then working on the subframe and trailing arms is improved tenfold...

charmalu · #8 08-30-2013, 12:08 PM

Isn`t 73 the new 55?

Iam 68 pushing 69

and still at it.

Dropping the whole rear suspension isn`t really difficult. If you have 3 floor jacks, a flat concrete work area you are golden. one jack under the Diff, and one under each trailing arm. once the DL, Shocks, calipers, brake cable is loosened, and the diff mount. It will just lower down and slide out with the floor jacks.

Once out, remove the 13mm bolt in the Hub and the 2 24mm (I believe) bolts that connect the arm to the Sub Frame and pull it off. slide the new one on and button it up.

Note:
I should say here that the vehicle should be securely and safely stable with jack stands before removing anything.

I used some 3/4" round stock, put it into the jack holes till it`s seated all the way in. then cut it off 4" or so past the Jack Hole, had it bent about 15 deg so it is level with the ground. then set these on your jack Stands to hold the vehicle.

Now if your Jack Holes are rusted out, HMMMM.... not sure what to do then.

STRETCH, you have that excellent thread on removing the assy. think I posted how I did mine step by step in a post.

GRAHAM, isn`t there some young Bucks on the forum that would pitch in from your area?

Charlie

Stretch · #9 08-30-2013, 01:47 PM

Quote:

Originally Posted by charmalu

...
STRETCH, you have that excellent thread on removing the assy. think I posted how I did mine step by step in a post.

GRAHAM, isn`t there some young Bucks on the forum that would pitch in from your area?

Charlie

Several people have contributed to the thread (your good self included). Here it is =>

Rear subframe removal and bushing replacement

Access to a two post lift would make this job a giggle - the greatest difficulty would then be reduced to rusted nuts.

Graham · #10 08-30-2013, 04:28 PM

Quote:

Originally Posted by charmalu

Isn`t 73 the new 55?

Iam 68 pushing 69

and still at it.

GRAHAM, isn`t there some young Bucks on the forum that would pitch in from your area?

Charlie

Thanks for the encouragement. I understand what is involved, but it looks like too much of a job for me.

Re the young-bucks - none I know of here in Great White North, but if there are, maybe they would like to buy the car

What I would like to do, before deciding on what to do, is lower the trailing arms so that I can inspect the top side where the springs are seated. Any good advice on how I can do that safely would be welcome! (Just did front on our smartcar, but it is like a golf cart!)

t walgamuth · #11 08-30-2013, 04:49 PM

I believe you should be able to get one arm replaced for 2 to 300, both for 3 to 400, paying an indy to do it. Used arems surely can be found from the south for $100 plus ship or less.

whunter · #12 08-30-2013, 09:35 PM

Quote:

Originally Posted by Graham

I was about to paint trailing arms on my 85 300D, but after scraping off dirt etc, noticed some pinholes. Looks like I have some rust. Tapping indicates arm is generally solid except in those areas.

Ideas that come to mind:
-POR/JBWeld plus spray interior with Fluid Film or similar.
- Weld repair
- Replace with good used.

I am about $2600 and 9 months into an overall rust repair. But, we don't NEED this car, so there has to be a limit.

What do you think about the repair options?

Replace it with a good used unit.

Here is what will happen if it is patched up.
http://www.peachparts.com/shopforum/body-repair-restoration/220623-1985-300sd-rr-trailing-arm-rust-pictures.html

.

Graham · #13 08-30-2013, 09:44 PM

I have a question about the lower shock mounts. In the picture I posted, it looks like there are bolts with nuts on bottom. Maybe they are welded studs?

In sketch below from manual, it looks like there are studs screwing upwards into what looks like square nuts likely welded to trailing arm?

If I want to remove shocks, if those are bolts, it might be a trick to hold the heads.

PS: Bill H. - I agree that replacement trailing arm is the right thing. But up here we have no used MB parts sources. Just looking at all possibilities. The trailing arm on my car is nowhere near as bad as the one you linked. But it could be with no attention. At present I am in inspection mode and would like to get shocks and springs out of way and have a better look at top side.

whunter · #14 08-30-2013, 10:19 PM

Quote:

Originally Posted by Graham

PS: Bill H. - I agree that replacement trailing arm is the right thing. But up here we have no used MB parts sources. Just looking at all possibilities. The trailing arm on my car is nowhere near as bad as the one you linked. But it could be with no attention. At present I am in inspection mode and would like to get shocks and springs out of way and have a better look at top side.

If you can get to Detroit?
I have trailing arms for sale.

.

Graham · #15 08-30-2013, 10:33 PM

Quote:

Originally Posted by whunter

If you can get to Detroit?
I have trailing arms for sale.

.

We are at far east end of Lake Ontario, so Detroit is not too handy. I have had some large items shipped to border pick up point in NY state, but maybe shipping these would be difficult?

Out of interest, what is the price range for used trailing arms?