I disassembled a Shimano XT rear der, and removed both upper and lower pulley wheels. During the vigorous cleaning of the upper pulley (the one with ceramic bushing), I removed the rubber seals hidden under the steel covers.
The problem is the seal needs to be installed so its configured in a pleat-like fashion. Essentially, the rubber seals inside diameter is roughy 1.5 times bigger than the groove. So the pleating is necessary to fit the groove. I recall seeing this pleat-like configuration when I disassembled it, but didn't give it much thought until it was too late..
Has anyone replaced this seal with success? If so, what is the trick. I tried inserting the 12:00 and 6:00 positions, then 9:00 and 3:00 positions, but just can't make it happen.