Motorcycle Repair: gear oil, odd ounces, cb900 custom

Question
I have a cb900 custom honda--1980--30,000 miles and I,m wanting to change the gear oil in the subtransmission--least I think that is what it is called(dual range transmission)anyhow the manualand the sticker above the fill hole say to use --hypoid gear oil SAE 80 ONLY--well I can't find in 80 ONLY. What I need to know is would 80w85 or 80w 90 work? Even at the local honda shop they did,nt really seem to know what I was talking about and they gave-or sold- me a small 8oz bottle for the drive shaft--book calls for 20 some odd ounces for a change--Thanks for any help

Answer
Hi Bill.
 Did you check in the auto parts store?  I see that grade of oil all the time there.

 The dealership parts guys won't know about it because the bike is probably older than they are, so they won't be familiar with it.
 The mechanics may know what you are talking about and could be of more assistance to you on this.

 To the best of my knowledge, there is a difference between SAE80 and 80w85 oil and you shouldn't mix the two as they are for different applications.

Sorry that I cannot help you further.
Good luck.
FALCON