Right Onetim! I had forgotten about that one, even though my Mini had that leak - about the easiest to fix.

Another real common oil leak is where the shift rod shaft goes in the transmission on a rod type shifter. This type will not have a long aluminum housing back to the shifter. there are kits to fix this.

Thanks you much for the info, will put it on the lift this week end, no leaks on top of engine, have to remove skid plate to visualize the bottom of engine

Judging by your avatar photo, you are referring to a classic Mini, so, yes, the engine and transmission share the same oil. You should be using 20W50 or 29W40 oil.

If you look underneath, there is only one drain plug - the transmission case acts as an oil pan.
If you remove the drain plug, be very careful putting it back in - it is very easy to strip the threads in the aluminum gearbox.

Don't panic. Almost all Minis drip oil at one time or another. You need to jack up the car and get under there - with proper jack stands - and figure out where it is leaking. Here's a starting list of where leaks occur:
- valve rocker cover
- tappet covers  - your engine may or may not have them. They are below the intake and exhaust manifolds.
- differential case where the driveshafts come out.
- pot joints - if your car has them
- front crankshaft seal - behind the crank pulley
- rear crankshaft seal - inside the clutch housing, and presents as drips of oil coming off a cotter pin hanging out of a drain hole on the clutch housing. The cotter pin may be missing - it's purpose is to rattle around and keep the drain hole open!
- head gasket leak
- gasket leak between engine and transmission
 - somebody else's oil drip.

Sometimes Minis drip if left parked too long. They don't like being ignored!

Since Im still a Rookie the gear box and motor use the same oil, I developed a pretty good leak from under neath?  Or does gear box have a heavier weight in it