Where is the filler cap for this 1980 Ford 1920 series for the hydraulic system

[SoulRavenWolf]

I bought a used Ford 1920 series tractor .2 days ago I blowed a line left it in the field a d replaced the line but can't fi d the filler cap for the hydraulic system.

 

[D&D]

Just to the right of the gearshift, there’s a black rubber plug. That’s the hydraulic/trans dipstick. Behind the seat, there should be a fill plug

 

[TractorTech]

Just to the right of the gearshift, there’s a black rubber plug. That’s the hydraulic/trans dipstick. Behind the seat, there should be a fill plug

No plug behind seat, just the one on the transmission. Transmission, rear end and hydraulics are all together.