53 New Yorker Gear Oil and Fluid Drive Oil.
 

This car has not been driven since 1964. I am wanting to change the transmission and gearbox oil. The manual calls for Extreme High Pressure Hypoid 90 for the gear box. Most of what I have found is 80w-90 Is that the same? Will the new oil damage any seals or parts? As for the transmission, some say 10W motor oil will be fine, so, 10W40? I have only driven a half mile for a short test and had no problems. Because it is so old, I don't want to go down the, "if it isn't broke don't fix it road"
Thanks, Steve.

Is the fluid drive a hydraulic oil not motor oil?

Manual states SAE 10W engine oil. Trans is a C-60 Fluid Torqe Drive. I assume 10W-30 or 40 will be fine. I found some Premier GL 1-90 gear oil but it does not state High Pressure, which is recommended for Hypoid gears. All others found for Hypoid are 80W-90. Just trying to understand before proceeding.

I would run what the factory service manual said to run.
But if your looking for a great 80W or 90W.... Torco is the way to go >>>>> http://torcousa.com/torco_product/mgo.html