So, this is a first for me. Has anyone else seen on of these?

I've never been inside a Z transmission, let alone an early one. But just because it's been 19 hours and there's been no action...

So what is it I'm looking at here? Is that the 5-R section of the trans, or is that an unsynchronized first gear? (Did they use an unsynchronized 1st gear version on the trucks of the same era?)

I have never opened a truck 4 or 5 spd. This one has a different fork, gear and has a spring to push the syncro into place.

It looks like a heavy duty straight cut reverse gear.

But why is it there?

For going backwards?

Looks to me like a standard 620 truck 5 speed FS5W71B from the model 76-79.

You can find it in carpartsmanual

 

I've read the 620 transmissions might be shorter.  Can't tell much about that one from that single picture.

Funny, but the gear is the same part number for both, until later, with overlap from 76 - 78.  Interchangeable.  So it could be a truck gear in a 280Z if I read right.

https://www.carpartsmanual.com/datsun/pickup-1972-1979/power-train/transmission-gear/5-speed-(from-aug-76)/41

http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/transmission-gears/5-speed/40

That’s a new one on me. 

Looks like that main shaft nut has been off and replaced at least once. Looks like a spot weld has been added...

Just realized that I didn't really absorb the full title of this thread, I just l saw 280Z and looked at the picture.  It says "1st gear" in the title but the picture is of overdrive (5th) and reverse.  Not sure where the mixup is happening, if gnozez posted the wrong picture or just got turned around mentally.  It happens.