Hi filler plug is pipe plug on top of transmission cover by gear shift lever.
Full check plug is on side of transmission case by right foot rest and left brake pedal.
Use 90W gear oil, capacity is 4 Imperial Gallons (5 USA Gallons).
Note: if this was an Industrial version B-414D it may have IH Hytran in the transmission,
so do a check at the Full check plug and see if current oil is thick black gear oil or thin IH Hytran?