I thought the rear main is a rope seal.

I don't have any experience to help, sorry.

Does this thread give you any clues?
http://www.peachparts.com/shopforum/diesel-discussion/298852-rear-crankshaft-rope-seal-replacement-without-removing-crank.html

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'84 190D 2.2 5MT (Red/Palomino) Current car. Love it!
'85 190D 2.2 Auto *Cali* (Blue/Blue) *sold*
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