Oil from transmission vent

My 2188 leaks also but not as bad as you describe. I don't have a 2 speed so that is probably ruled out. My thought is that oil from the hydro is leaking into the transmisson and "over filling" it. Don't know if it's possible but just a though.

Maybe someone with more knowledge will tell us.

Either the hydro motor seal is leaking or the brakes are leaking. Either is possible. I have seen the hydro motor seal go out, and other guys on here have seen the brake seals go out. Both do the same thing.

Had this problem with a hyd. tank on a Ford bi directional.
Raised vent 6 inches-problem solved.The vent on some hyd. tanks and gearboxes is too close to oil surface causing oil to come out when it heats up and expands and is sloshed around due to unit movement.

It is likely one of the brake units leaking on the transmission. They only pressurize when the park brake is released during travel. When park is applied or combine is shutdown the oil supply to the park brake packs is cutoff and the springs mechanically apply the brakes.
Talk to a Case-IH dealer there is a quick test procedure without teardown that will confirm which unit is leaking. The least expensive repair is a reman brake unit forget trying to rebuild yourself. Individual repair parts cost more to repair old unit than the reman unit with warranty and your core returned.
The hydro seal could be leaking but it will only leak when moving not standing still, the brakes will continue leaking with the park brake turned off and combine standing still with the engine running.
If you pull transmission drain plug and run combine standing still with park brake off and oil runs out the drain plug you know it is a bad brake unit. Good Luck.

Thanks everyone. Guess we'll have em check it out when it goes in for its checkup later this year. We figured it would be some type of seal failing, but didnt know which one or where to start. Just have to wait and see now i guess.

10-4 on the brake probably the right one fortunately for you with a 2188 you won`t have to pull the tranny to fix it