Hydro motor seal question
 

I'm still learning the hydraulics setup on this stuff. I have not had the opportunity to actually touch or dissemble a pump. I'm thinking of making my own but need to figure out what is being used or done to seal the motor shaft in the pump housing? A lot of what I've seen (I think) motors have small shafts, pressed on gears? But I can't find any such small rotary seals to be used. Pics would be appreciated :)