6518 questions

[MarksA-C 93]

I plan on taking a short "Break" from the 610 to get at least 1 tractor ready for winter. The 6518 is ok right now, but the trans is leaking oil and not giving as much power as before. I think it needs some help. Also, I think I should change the oil to something a little more...Winter friendly (Maybe a synthetic?) I also have to finish adding all the last few nuts and bolts that hold the thing together.B) Here are my questions... 1) What kind of oil could I use in the Eaton 850 trans? I hope to get a synthetis because the oil I have in it is think enough that even at 50 degrees it bogs down the engine when I engage the trans. 2) Are there any problems I would have to watch for when I take out the trans? Any hidden bolts or secret wires that might cause problems? 3) What oil filter can I use to replace the Fram junker? Yeah, not a good buy on my part. All info would be great. Thank you