GM-GMC: rear seal leak, chevy diesel, diesel motors

Question
i just bought a 1985 chevy diesel truck. the truck has been setting up for about 6 mouths and now has a rear seal leak. is there a additive i can use in the oil to stop this leak? i dont know much about diesel motors but i guess i am about to learn.  

Answer
Lee,

The rear main seal design on your diesel is exactly the same as  Chevy has used on all its engines for decades.  It is a rope seal and they inevitably go bad after so many miles or years.

A two-piece rubber seal is available and it can be installed without removing the engine.  The oil pan has to be removed, which may require lifting the engine if you have a C series truck, but no engine lifting is required if you have a K series.  I have one of both.

I would not use an additive to stop such a leak.