i had a seized caliper on my 81 240d, rear right side- the rubber around the pistons were toast, so i decided to replace with a reman caliper- and a new rotor since the seized caliper destroyed the old rotor...
anyhow, it took some PB blaster and a rubber mallet to get the old rusty rotor off... but eventually it came off. after getting the new rotor on and the new caliper attached, i noticed that behind the wheel hub i could see some sort fo bearings... where the rubber boot part meets the wheel hub... the other rear wheel doesnt seem to look this way, and i can't see why a bearing would be exposed, so i assume this is a problem!!
sorta like the whole wheel hub assembly has pulled out exposing the bearings. i've attached a few photos so you see what i mean. i am not sure if it was like this before i took off the old rotor/caliper, or if I caused it to happen when banging the rusty old rotor off... i gave the hub a few taps with a rubber mallet to see if that would reseat/push it back, but it doesnt seem to budge...

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1981 240D ... 265k
1977 240D ... 265k
1977 240D ... 250k