My 440 coronet has an oil leak I believe is coming from the rear main. Can too much oil pressure cause this. Going down the road hot 80lbs. Up to 100lbs when cold. It has about 45lbs at idle. It's already blew out the oil sending unit. I run 10w-40 oil. Thanks for any input

Most of the Hi Po oil pumps(high volume also) I've seen and used had a bypass pressure of 80 lbs, I normally cut down the bypass springs so I can have 75 lbs at 7500 RPM with hot, thin(5W20WT ) oil. That set up will have 80 lbs cold at or above 1200 RPM, it will have between 18 to 25 lbs at 850 RPM with the same oil at or above 180 F That will provide close to 75 lbs at 7500 RPM with 150 F or under oil temps. As far as making the rear main leak the crankshaft flange should divert any high pressure oil being squirted directly onto the rear main seal itself Look very closely at the back of the crankshaft flane and the front side of the flexplate or flywheel, if the oil is coming out of the rear main seal it will be flung onto the crankshaft flange and be flung outwards onto and outwards on the front of the fleplate or flywheel. If the sides seals or the gally plugs or cam plug are leaking there won't oil be on the front of the crankshaft flange and flexplate like when coming from the main seal They can leak onto and usually are signs of oil on the oil pan rails and some can blow onto the flexplate of flywheel if you don't have the dust cover on the bell housing IHTHs

Carefully check the pan and pan bolts for leaks,we see many that people think it's the rear main seal and it turns out to be the pan,bolts or side seals.

Put in lighter weight oil to knock down some pressure
but check like the others said