Massey Furguson industrial 204 - engine runs, but wont move forward or backwards

[onlinefunner]

Engine revs up and down fine too. Was working fine a few weeks ago, then last week it had the same issue for a couple minutes after starting, but now wont go anywhere.

My only idea is it's low on some sort of fluid, but the manual is a bit confusing to say the least.

I did open the bolt on the right side, thinking it was the filler hole for the "Reverse-O-Matic and Torque Converter fill and oil level plug" but some brown liquid started pouring out fast, so not sure how this is a fill hole.

Any other ideas?