Wet Brake question

Hello All,

I have just acquired a Branson 4220 and the previous owner removed all plates within the brake housing. this is the first tractor (aside from a LT) I have owned and do not understand the wet braking system.

some of the reading I have done, kind of reads as the wet brake is getting it's fluid from the hydraulic system/reservoir. other posts kind of read as though ALL fluid beside cooling is the same (Tranny - wet brake - lifting - 3 pt). I did not receive a manual with the tractor but I found some spec's stating 37 gals of hydraulic fluid????? holy cow, is that correct?

so if the wet brake does get it's fluid from the hydraulic reservoir, I am assuming it will just get pumped in when it is running. or do I need to prime it after putting things back together?

more questions to follow and I greatly appreciate the help!!!!!
MTF helped me greatly bringing a 62 Gravely back from a 20 yr sleep, so I know I am on the right forum