You can unscrew the outer cap or the allen plug on the hub to drain.
If you have reliable oil bath hubs.
Bearing Lubrication – Oil
Below is a listing of approved lubrication
for all Reliable hubs and drums using oil
(Only to be used when unit is equipped
with the Oil Bath Lubrication System)
Valvoline Gear Oil 80W-90
SAE 90 Hypoid Gear Oil
Exxon Gear Oil 80W-90
There was also a change in the reliable documentation to fill the hubs completely full.