[hogdad]

Why does the uce left case have an oil filler plug?
I thought the entire lubricating system (engine, clutch, and transmission) was filled from the right case filler plug.
Does the primary chain in the left case sit in an oil bath?
If so, is it fed from the main sump or is it separate?

[Ragmas]

That is an inspection plug.  It also aides in removing that case side if you have the proper tool.  You could put oil in there but it is not necessary.  Leave it closed.

Samgar
 

[gremlin]

Why does the uce left case have an oil filler plug?
I thought the entire lubricating system (engine, clutch, and transmission) was filled from the right case filler plug.
Does the primary chain in the left case sit in an oil bath?
If so, is it fed from the main sump or is it separate?

the primary chain runs in the same oil as the rest of the powerplant.
it is fed by the main sump.

the left plug is used to inspect slack of the primary chain.

having said that, I suppose it could be used to refill the sump following a filter change.