I believe this has a Peerless 801 transmission, and unless you see leaks where it's parked you may not need to fill it. Overfilling a transaxle can be bad for it. I would check with nearest Jon Deere agency.
you can not fill the transmission on a JD 155c, it is sealed.
John Deere 450H Dozer hydralic transmission how can drain
I the cab. The transmission fill also supplies all of the hydraulics.
what type of fluid does a john deere transmission transfer case use
Where is the transmission oil container located?
Hydrostat Fluid
next to were you fill your gas under seat, left hand side
John Deere recommends that you put Low Viscosity Hy-Gard or Hy-Gard Transmission oil in their Hydro or Gear Transmissions. The Low-Vis is used for factory fill in the Hydro and Hy-Gard in the Gear Transmission.
Use any Automatic transmission fluid type F, or use John Deere low viscosity hydraulic fluid
type F
John deere hy-gard or any good trans. Hydraulic oil
John Deere all-weather hydrostatic fluid or an equivalent type "F" automatic transmission fluid