LOUD whining noise after Rear Main Seal replaced

[13Dhex]

Hello All, I am new here to the forum, and relatively new to working on cars.

Last week I bought a 79 350 V8 4x4 with a 4-speed manual transmission for $600!

The main problem with the truck is that it was leaking oil at the rate of a big drop per second(only when the engine was running). The previous owner was pretty certain that it was the Rear Main Seal.

So, this past weekend I tried my hand at replacing this seal, and everything seemed to go well. Then when I cranked her up, there was a LOUD whining noise, it didnt go away after 2 seconds so I quickly turned her off fearing doing damage to the engine.

Any ideas on what this may be, and what steps I should take moving forward?

Thanks!