The serial number will be one of two places. Early ones will have the serial mounted on the right side of the transmission case down by the right brake area but near the top of the case. Later ones 52 &amp; up the serial number tag ill be on the dask toward the operator but on the left side. 80-90 Gear oil is good. If same capacity as a rowcrop, buy a 5 gallon bucket of it. It takes about all but 1 quart.