Oliver Super 55 fluids change help needed

I recently purchased a Super 55 that was not very well taken care of. I am in the process of trying to drain and replace all of the fluids. I drained the engine oil and cleaned out the oil bath air cleaner. I removed all three drain plugs under the tractor and not much fluid came out. What are each of them for? How do I refill them, with what fluid and how much? Also, there is a small dipstick near the seat that has foamy fluid but I do not know how to drain this. Any help would be greatly appreciated!

Congrats on the new purchase. Order an owners manual as it will cover all the regular maintenance. I have a 1973 Oliver 550, but maint. items should be the same.

- Engine oil - Capacity 4 qts, I use 10W-30, filter right side of engine.

- Transmission - The 3 drain plugs under the tractor drain the transmission. They all drain the same fluid from the 3 shared sections - transmission, differential, final drive.
Capacity 5 gals. 80W-90 gear oil. (Manual states 10W-30 oil, but I've always used gear oil). Filler cap is the slotted cap between your knees, just in front of the hyd. filter that
faces front. Check plug is square pipe plug on the rear, just to the right of the pto. Fluid should be at the bottom of level of the plug hole. The manual suggests flushing the
transmission, which might be a good idea in your case since it sounds pretty empty. It states pour 4 gals. of kerosene into the transmission and operate the tractor in all speeds
without load for 5 minutes before draining and flushing solvent. I have done this in the past and did get some crud out.

- Small dipstick with foamy fluid is the hydraulic fluid to run the three point lift. The fluid is contained in a separate section above the transmission, there is a steel pan
separating the two. If the pan develops holes you may notice the hyd. level decrease and the transmission fluid level increase. That dipstick hole under the seat, right side, is the
check AND fill hole. Capacity approx. 9 gals. I use universal trans-hydraulic oil .
To drain (depending on any aftermarket equipment - mine has aftermarket valve and rear hyd. hookups). Lower 3 point all the way. Remove the 1/4 pipe plug from the hyd. passage cover -
right side of hyd. cover, just behind hyd. filter - install a piece of 1/4 pipe nipple, start the engine, let it idle as it pumps the hyd. fluid out. Have a 3 gallon container to catch
it all. Fill through dipstick hole. Replace hyd. filter in front of seat. The cast cover about the size of a pop can unscrews and the filter element is inside. Only available from
AGCO dealer, part# 100-476-ASA

Good Luck,
SW3

SW3 was pretty thorough on the explanations of the different oil. If your hydraulic fluid is foamy, that is cavitation and can damage your hydraulic system. May be due to low level.
Make sure you correct that.