I think this applies to 123's also. Having to replace the brake cable on a replacement trailing arm for my daughter's 84 300SD and not finding a clear explanation of the necessary steps, I thought I'd write up a brief description. These are necessary steps. The brake shoes do not need to be completely removed.

Loosen bolt holding the bracket for the cable on back of hub.
Remove one end of the spring holding the shoes together at the cable/expander end of the brake shoes. I don't think the spring can be completely removed until the expander is pulled out of the way, but removing the spring completely is not necessary. Note the orientation of the spring. It is not symmetrical.
Pry the shoes back from the expander. Mine stayed back once I pryed and pulled them out of the way.
Loosen the two allen bolts which hold the cast metal piece above the expander. (or below--mine was above since I was working on the trailing arm outside the car) It requires a 7mm allen wrench inserted through one of the lug holes. A 7mm wrench is uncommon. I was only able to find one set among the many at HF which had a 7mm.
Remove the bolts and loosen the cast iron piece. The cable runs thru a hole in the cast iron piece so it can't be completely removed.
Pull the expander out away from the backing plate a few inches. This requires the cable to move thru its casing. The brake shoe spring is removable at this point if necessary.
The cable has a clevis on the end, pinned to the expander. My pin dropped right out easily.
Once the pin is out you can remove the old cable and insert the new one.
Put the pin back in the clevis, push the cable and expander back into place, reinstall the cast iron piece, put the shoes back on the ends of the expander and reinstall the spring. (the spring is not symmetrical. Note how it goes before removing it intially)

The whole process is not difficult but it's not immediately obvious when you first look at it. It appears as if it might be possible to remove and replace the clevis without disturbing the rest of the brake system.. It's not. The pin holding the clevis will not come out without disassembly. It also looks like you might be able to pull out the expander without removing the cast iron piece. You can't. The allen bolts holding the cast iron piece were very tight on mine. It took a 2' pipe on the end of the allen wrench to break them free. You'll be working with the short end of the allen wrench since the long end has to go thru the lug bolt hole to reach the allen bolt. I haven't re-installed the spring yet but I think it's possible without any special tools. I'll probably use needle nosed vice grips but I did buy a little hooked puller when I picked up the 7mm allen wrench at HF.

Edit: I was able to reinstall the spring without any special tools. I used a hemostat to position it and a needle nosed vice grips to pull it into the slot, pushing it the last little bit with a flat screwdriver.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Great DIY write up.

I swapped out the Trailing Arms on our 85 300D several years ago with a set off a lower mileage 300CD.
I just cut the cables off behind the Backing plate, Iam cheap and didn`t want to pay for them too.

Should not have done that, as I remember it was a PITA replacing the cables.
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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Nicely done write up. Thanks.

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1983 123.133 California
- GreaseCar Veg System