Engine oil trans oil

Is the primary oil engine oil or transmission oil? Lost here.

The Primary is fed by the Trans oil . Or better put , when you fill your trans you are also filling the primary. The oil flows between both trans and primary.
 
Thanks Tony! That was the answer I was looking for. Most of my bikes have engine/trans oil mixed together. My buddy's HD has a different primary & trans oil.
Older Nortons have a separate trans with it's own oil. Correct?
 
Thanks Tony! That was the answer I was looking for. Most of my bikes have engine/trans oil mixed together. My buddy's HD has a different primary & trans oil.
Older Nortons have a separate trans with it's own oil. Correct?

Yes for sure. The Vintage Commando has a separate trans lube , separate primary and separate engine oil
 
"Same oil. Just separated. See my manuals on oil changes." richard-7 says. TonyA has an other opinion. What's the true?
 
The oil in both engine and gearbox is the same specification and grade, it is just in separate compartments so need to be drained and refilled independently (but at the same time).
 
Thank you, Rob. Based on Norton original manual I understood it so.
 
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