I had an oil leak from my 92 9000 T. It appeared to be combing from around the filter mount. I bought a new o-ring for the oil filter mount from Mile Hi in Denver.
Replacing it was much easier than I anticipated, although having a lift would have been nice. I used a 1 1/16 socket (I did not have the 27 mm but the 1 1/16 inch is 26.99 mm) and it came out and went back in pretty easily. I did this after draining oil and before refilling.
It seems not to leak any more.
Charles