So the plot thickens.

After a short drive, I decided to check the transmission oil, mostly to see what it smelled like, since a bad bearing will probably burn some oil, and the more burned the oil is, the worse the bearing (tell me if my logic is wrong). I discovered that the oil was low, below the minimum mark, so I topped it up.

Now the noise is very different, reminds me of a loud power steering pump without enough fluid. For the first mile, at low speeds, the noise was intermittent, which was nice, now it's presenting at the same times as before, but with the different sound than before.

I'm thinking pump? Which is replaceable, rather than the whole transmission? Or would going from low fluid to normal fluid change the noise of an input shaft bearing?

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1982 300TD 300,??? miles, daily driver turned donor
1982 300TD, 184,000 miles, daily driver