Rear Main Seal
A rear main seal is also known as a rear crankshaft seal. As its name says, it seals the rear end of the crankshaft where it exits the engine and connects to the flywheel or flexplate.
Since the only job of your rear main seal is to prevent oil leaks from the rear of the engine, its failure to operate will result in drops of oil found between the engine and the transmission. Besides, if you have a clutch it may slip or grab due to the presence of oil.
Rear main seal maintenance
Your mechanic will have to take off the transmission to replace the rear main seal, which involves an expensive labor. That’s why it is always a good idea to replace your rear main seal each and every time your transmission is removed.