Charlie's comments are good ones.  Sometimes the rear seal is NOT the actual source of the oil drops that you're seeing under that area of the engine.

Here are some links to previous threads about rear seal replacements.  Click on these links to have them open
http://forums.y-blocksforever.com/Topic118269.aspx#bm118270
http://forums.y-blocksforever.com/Topic114021.aspx#bm114031
http://forums.y-blocksforever.com/Topic106586.aspx?Update=1

The link that is shown below may have been referenced in one of the links above.  I list this particular one again because it speaks specifically to what you originally asked about.  IF you do need to 'fix' the rear seal, 'Is there a way to do it without loosening the main bearing caps to drop the crank to remove the upper portion of the seal?'  I've done this twice 'on the job' with 100% success.  What I'm not sure of was the thickness of the shim stock I used for inserting behind the upper rope seal.  It was not that thick, but likely .035+ inch.  My experience is that just dropping the oil pan, removing the lower rear seal retainer, replacing the lower portion of the rope seal and the side seals, shimming the upper portion of the rope seal, cleaning the oil pan gasket surfaces, 'adjusting' the perimeter oil pan bolt holes with a ball pein hammer, reconnecting the oil pick-up tube, and putting the new pan gasket and oil pan back on is enough work even when done using a floor lift.  Too, you only want to do this once!  Several years ago I reported that an acquaintance had installed three (3) of the newer neoprene rear main seals before resorting to successfully installing a 'Best' brand rope seal.  UGH!

http://forums.y-blocksforever.com/FindPost106604.aspx

Hope this helps.      


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

People have had success doing a seal replacement with the engine still installed.

The rear main seal is blamed for many leaks that are not from the rear main.  Before going through all of that work, be sure it is the problem.

These include but are not limited to:  valley pan, oil filter or adapter, oil pump, valve covers, bolt missing from the rearmost hole in the intake flange on the head, lack of thread sealer on the studs in the rear main seal retainer, side seals that were not trimmed when the rear main was installed, bent oil pan, cam plug, oil galley plugs.



Lawrenceville, GA

Has anyone ever successfully repaired a rear main seal leak by dropping the oil pan, removing the lower seal and tapping out (rubber/neoprene) or pulling (rope) seal and replacing with a new seal on a y-block?
I have the power steering out for rebuild and will be replacing the starter. There are 2 oil drip spots on some cardboard under the car: one coming from the very back end of the oil pan just after the oil drain plug and the other at the lowest spot on the front edge of the bell housing. if I drew a line between the 2 drips it would form a straight line down the center of the car. I assume the leak is from the rear main seal.
I am not a proponent of a snake oil remedy, but has anyone used a product called AT-205 Resealer which is supposed to be a seal conditioner. I have read more positive than negative reviews.

Thanks,
Danny