I've just done this job (because of wheel bearing issues) on a 123 240TD.
I didn't find I needed to drop the diff at any time, but I reckon that it's gotta be worth fitting new bushes if you've got the arm off the car cos its so simple to do...
good luck
Giles

Did you have to use a spring compressor? I found that the limiter-stop on my crossmember didn't allow the trailing-arm to drop enough to relieve the spring pressure. Lowering the differential a few inches tilted the crossmember and trailing-arm that extra bit, and allowed the spring to be lifted out by hand.

Happy Motoring, Mark

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DrDKW

I did this job last fall because of a rusted trailing arm and am also doing it again on another car to renew all the bushings and get rid of surface rust before too late. I removed everything on the first car and the current car to inspect/repaint while replacing parts, so I thought I'd add my experience.

I removed the entire "axle assembly" and it took me about 3 hours from driving the car in the garage and having the entire subframe/diff/trailing arms/halfshafts assembly out in front of me. About another 1/2 hour disassembling everything for cleaning and new bushings. I made a "pumpkin" holder (like in the shop manual) out of a 2x6, two 2x4s on the sides, and a large socket bolted to the bottom. The socket fits right into the top of my hydraulic jack where the normal steel cup fits and the entire assembly is secured with a rope to the differential. I also have a spring compressor, so I pretty much followed the manual step by step. No problems reinstalling the axle using the floor jack and it seems the center of gravity is fairly on top of the jack and is quite manageable.

I liked removing the entire assembly so that I could work on it away from the car and not on my back. It looks like you've got plenty of rust on your subframe as well, so maybe a good idea to clean it, remove the surface rust, and paint it if you have the time.

Good luck with that rust!

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Dave

2002 Audi S6 Avant
1983 300D
1984 300D (sold)
1990 560SEL (sold)

I presume that you removed the entire subframe?

Yes, all in one package.

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Dave

2002 Audi S6 Avant
1983 300D
1984 300D (sold)
1990 560SEL (sold)

My son and I just replaced both rear trailing arms in his '82 300D with used units from Potomac German Auto. The replacements came with bushings/bearings and emergence brake cables that looked and felt good so we just used them. As posted earlier (doing one side at a time) we jacked the car up, dropped the differential a bit, removed the subframe mounting bolts, and lowered the trailing arm (bottom shock mount had rusted through so shock did not limit downward travel. I left the shock in place until the end to help contain the coil spring should it want to jump out. With the trailing arm down we could lift the spring out by hand. Front trailing arm to subframe bolt was accessbile once the subframe came down in front. Only hitch was a that one of the big subframe bolts was seized in the bushing of the subframe mount. Destroyed the mount getting the bolt out but we replaced them both anyway. Not too bad, just dirty and slow. Should last another 24 years and the car rides a bit higher with the new subframe bushings in place.