W126 cracked trailing arm. Can it be safely welded? - PeachParts Mercedes-Benz Forum

#1 07-16-2010, 07:01 AM

There you go! A good used one would be less trouble, probably less expen$e and take away any concern you might have about your welding skill.

bolomiester · #2 07-16-2010, 07:26 AM

Quote:

Originally Posted by LarryBible

There you go! A good used one would be less trouble, probably less expen$e and take away any concern you might have about your welding skill.

I'm totally convinced that a good used one is the only way to go. Several forum members have contacted me saying they have one. I'm just trying to sort out who has the correct part at a good price.

So far I can't understand if all w126s use the same one or if they are different. Hopefully it will all come together in the next day or so. I'm anxious to get it fixed. While I'm at it I plan to install new shocks and thicker spring spacers to hopefully correct the camber.

Stretch · #3 07-16-2010, 01:46 PM

Quote:

Originally Posted by bolomiester

I'm totally convinced that a good used one is the only way to go. Several forum members have contacted me saying they have one. I'm just trying to sort out who has the correct part at a good price.

So far I can't understand if all w126s use the same one or if they are different. Hopefully it will all come together in the next day or so. I'm anxious to get it fixed. While I'm at it I plan to install new shocks and thicker spring spacers to hopefully correct the camber.

From what I have read here there are two types of trailing arms - steel and aluminium. Both fit on the w126 and w123 models.

Are you aware about the differential mount that can also cause sagging - I assume that is causing an incorrect camber on your rear wheels?

It is worth your while checking the length of your uncompressed springs before re-assembling your suspension and the thickness of your existing rubber spring mounts... I've just put my w123 suspension back together (front and back) putting back in 3 nub rubber mounts after replacing all of the other rubber components. Checking with the data in the FSM the "new" suspension was within limits.

300D85 · #4 07-17-2010, 07:10 AM

http://www.peachparts.com/shopforum/showpost.php?p=2386499&postcount=53

Quote:

From what I remember the later W123 chassis used the same 126xxx part number rear trailing arm as the 1st gen W126 chassis. At some point in time (79???) there was a change in rear toe spec for the W123. The early W123 chassis also used the 115xxx part. So, I assume only the toe spec was changed. I doubt it will offer any more negative camber. I guess one could make encentric bolts/washers for the bushing holes.

bolomiester · #5 09-06-2010, 11:53 AM

I was able to locate a used right side trailing arm, and installed it along with new bushing for both sides. We also replaced the original coil spring shims with new ones that are 14mm thick v. the 9.5mm originals, and new Bilstein comfort shocks. The last step was to have a wheel alignment done.

The rear whels now have the same amount of negative camber. I'm not sure it's the correct amount, but it does look right, and the car no longer has a pull to the right.

I took the car on a 600 mile trip a few days after it was finished and, interestingly enough, the car's mileage improved by 1.5 mpg.

Thanks to everyone that offered advice. Welding was clearly not the way to go. As bad as the rust on the trailing arm looked on the bottom, it was far worst on top. Almost like swiss cheese.

The rust thing is a real mystery. It was only this part and the bracket that holds the fuel pump, fuel acumulator and fuel filter that show any sign of rust, and they were both very badly rusted, the car is otherwise rust-free. ????