If the oil is spraying the under carriage, above the transmissions drive shaft flange/ rear seal; it’s the rear seal.

Remove the cross member and check for any washer or shims, note there location.
Make a reference mark from the flange to the tail of the transmission and from the flex disc to the flange. Unbolt the flex disc and drive shaft center support then move the drive shaft to the side. You well need a thin wall deep 30mm 12point socket or equivalent in inches to remove rear nut. Once the nut is remove just pull the flange off. There’s a shin
Between the flange the rear bearing, do not loose it. Change the seal and put it all back together. Torque the nut to 89 ft. lbs.