Ford F53 transmission

I've never done the F53 transmission, but I would assume it's just like a car or pickup for that matter. There may or may not be a drain plug, most likely not. When you shimmy under the vehicle, take a large pan and rags with you. Loosen the bolts around the transmission pan and the fluid will leak out, naturally. Once the majority of it is out, remove the pan and clean the filter surfaces. There will probably be metal shavings in the pan - this is normal unless there are a LOT of them or large pieces. That's actually the main reason for changing the fluid, not that the fluid should be broken down by now unless you have a habit of heavy towing and transmission overheating. Once all is clean in the gasket area, install the new pan and gasket (depending on the type of gasket you may need to use some sort of gasket sealer), torque the bolts back (I would suggest using a 1/4" drive socket so you don't accidentally snap something off) and fill it with fluid. You'll most likely have to add the last of the fluid with the vehicle running in order to get it distributed throughout the transmission and the level reading properly. Remember that there will always be something left inside the transmission when you drain it, so if it shows full before you put the specified amount of fluid in, stop adding fluid and check it after you drive it for a few miles. You don't want to overfill it or it will cause foaming - not good. And remember to wear old clothes as the fluid usually goes wherever it wants when you loosen the pan up. Good luck!