Rear Main Seal

[explorer99sport]

I changed the oil on my truck and i realized there was some oil on the bell housing and where it mounts to the engine. there is no leak on the ground and when i check the oil every other day there is no loss in oil level. Should i replace the rear main seal or could it be something else?

 

[BrooklynBay]

How do you know that it's leaking from the rear main seal? It could be leaking from a gasket.