Idunno, I really can not tell you too much about the information you are searching for. In my post I asked some of the same questions, but not all were answered. In regards to the chain case and the hydraulic tank being separated, I believe you are correct. I can't see how the two could be connected without a lot of contamination to the hydraulic system. If I am wrong I hope someone with the knowledge and information chimes in. If your 1993 1840 has a chain oiling system similar to the one on my 1992 1845C, I believe you will find an oval shaped panel approx 8" long and 4" wide on each side of the floorboard fastened down by wing nuts. This is what I located on the 1945C, and believe they are where you add the chain lubricant. Now, what type of oil and how much is still a mystery. I would really like to come across a repair or parts manual that won't break the bank. I am still trying to find hydraulic fittings information about the couplers on the auxiliary hydraulics on the 1845C. If you read my post you will notice that I want to attach a western plow to my unit. The problem I am having right now is trying to determine what fittings I need on the plow hoses that will connect to the auxiliary hydraulics. I do not have the flat faced couplers on the loader. I know from the information that was provided that I will need flow restrictors on each plow hose to slow the angle speed. Maybe the solution is something as simple as changing the coupler and connector on the auxiliary hydraulics to match the present Western fittings. I hope someone a lot more knowledgeable than me responds to you post and gives you the correct scoop. Pat.