1962 Other Chevrolet Models trans lube on 1948 Fleetline

I'm assuming this is a stick shift trans. There should be 2 plugs on it, both under the car. One will be on the very bottom and that is the drain. There will be another one on the side which is the fill. You can use any grade of 80w/90w gear oil incuding synthetic. Todays oil is much better thatn the stuff they used then. Fill the trans until you can feel the oil with the first knuckle of your baby finger in the fill hole. In other words if you tip of your finger gets oil then it's full.