That tractor does not use transmission fluid. It uses gear oil for the gearbox and hydraulic fluid for the lift.
finger it
Mobil 424 hydraulic transmission tractor oil or Amsoil tractor hydraulic transmission oil
you can not fill the transmission on a JD 155c, it is sealed.
Dipstick on transmission top-right
how transmission oil capacity
Transmission fluid
The hydraulic fluid capacity of Case IH MX 170 tractor is 25.5 gallons. It's important to use enough fluid or the transmission could be damaged.
Tractor hydraulic fluid is usually an ISO 68, dextron III is equivalent to a 56 so it is probably too thin.
Coolant should not be leaking from your transmission the only fluid in your transmission is transmission fluid. A faulty transmission seal can allow transmission fluid to leak out.
Drain out the transmission fluid and replace with the correct fluid. Some types of transmission fluid are incompatible with other types of tranmssion fluid or with the transmission itself, and can destroy your transmission.
The transmission fluid should be change every 30,000 miles