I had this on my 300Tdi.
It is possible that the breathers on the top of the diffs are blocked and the pressure build up is causing the propshaft seals to leak oil. I checked them by removing the filler/drain plug and blowing down the breather pipes, I found that the rear one on mine was blocked.
If this is the problem there are kits availiable to fix this.
I solved the problem by purchasing a coil of nylon tubing from a local compressor/pneaumatic dealer(think it was 4mm i.d. and cost £8.00 ish for 30m). I removed the breather from the diff and cut the old pipe from the nipple. Soaked the breather in Jizer to clean it, warmed the nipple with a lighter and forced the new nylon pipe on.
While replacing these breather pipes I also did the transfer box and gearbox as well, and, extended them up to the air filter box so if wading there is less chance of water finding it's way into the diffs.
Don't know about the fuel sedimentor though.
Nigel