I just did this today. Remove the drain plug located on the bottom of the rear axle. The reservoir contains 5 qt's when full. Add Transmission Fluid to the filler hose located just above the dash under the hood.
John Deere 450H Dozer hydralic transmission how can drain
what type of fluid does a john deere transmission transfer case use
Hydrostat Fluid
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
7.2 quarts
Under fan
you can not fill the transmission on a JD 155c, it is sealed.
low viscosity Hy-Gard Transmission and Hydraulic Oil
10w-30 2qts