Customer Service Rep
The front main seal goes behind the crankshaft pulley on the passenger side. The REAR main seal is on the transmission side. Its possible it can leak after a certain amount of wear. Most good mechanics will replace that seal if a clutch job is done, or whenever the transmission is off the car. If your clutch is slipping its possible its from oil from the rear main seal (you can remove the inspection cover and look inside) however, if it is leaking inside the transmission it should be present at the bottom of trans, or leaking. Its most likely that your clutch is just slipping because you have exceeded the holding capacity of the clutch.