Thanks Mike, that helps a lot.
But now the plot thickens. I picked up this tranny at PickNPull the other day, from a '77 280Z.
- PickNPull tranny Apr2014-1.JPG (170.23 KiB) Viewed 3116 times
- PickNPull tranny Apr2014-4.JPG (161.44 KiB) Viewed 3116 times
- PickNPull tranny Apr2014-3.JPG (150.63 KiB) Viewed 3116 times
It had no shift knob or diagram. I ran it through the shift pattern and couldn't get it into 5th. Reverse was a tough shift too though, so I figured 5th is probably just old and baulky. Present, but not working. (Obviously I wasn't excited about that-- but I hoped that a rebuild could sort the problem out.)
But after I got it home, I did more research and found out that the 5-speed was an OPTION in '77. I hadn't known that. I thought that any manual tranny I came across in that year of 280Z was a 5-speed. (Stupid mistake, but there you are.)
So I tried to shift the darned thing again, and again only came up with 4 speeds, plus a somewhat stiff reverse.
That's why I asked the question earlier, whether you can visually tell a 4-speed from a 5-speed, coming out of a '77 280Z. Your pictures tell me that I've got a 5-speed. But I can't actually "find" 5th gear!
BTW, this was (is?) going to be a spare tranny. I already have a 5-speed from a '79 280ZX in my 510, so I'm pretty sure I know what the shift pattern is, and how they feel when they shift, etc. I don't think I'm trying to use a non-existent shift pattern!
Ideas? Suggestions?
... but let's say you can't actually shift the thing. Is there a way to tell just by looking whether it's a 4-speed or a 5-speed? Or do they use identical cases with only the innards being different? 
Not until seeing your note, that is. Bingo, that was the issue alright. A little spin of the shaft and-- magic!-- 5th gear appears out of nowhere! 