Zed Head

Could also be that the detent balls (check and interlock) in the adapter plate are damaged, or the notch in the shift rod. They are supposed to hold the forks in the proper position in each gear, and neutral. That fork is way out of alignment.

It probably could, on the steel forks. It would take some precise machining I think to grind the new surfaces flat and parallel.

Look at post #9. They can wear out. Too much hard shofting maybe.

No offense, it just seems goofy to wade through old threads just to say "welcome". Besides the insincerity.

Is post count a requirement for starting a picture gallery? Maybe @Mike can give you a waiver so you don't have to dig...

Another mystery company. Megazip. https://www.megazip.net/zapchasti-dlya-avtomobilej/nissan/280zx-2130/s130-6259/s130-182373/transmission-shift-control-2307215

More https://www.nissanpartsdeal.com/parts-list/1981-nissan-datsun_810/power_train/transmission_shift_control.html

And, it looks like other models used the same parts. No surprise, but expands the possibilities. Also says that the part number has been superceded by 32805-Q0101. IF the E9001 is the right fork. Could be the E9000. https://www.nissanpartsdeal.com/oem-nissan-720_pickup-shift_fork.html

I don't know what this company does but they have the part numbers. 32805-E9001 https://mmerlinn.com/catalog/dox_angel/dt_w7b/dtw7bp23.htm

Why?

core

Get a good small box end on a nut then turn the driveshaft by sticking a long screwdriver through the u-joint yoke. The wrench will jam against the body and break the nut loose as you turn the driveshaft. There are fine details to that description but that's the basic method I used to use.

carpartsmanual says the 4 speed forks will work, if you get the right 4 speed. It also says that you might get the wrong 5 speed parts, and be in the same pickle. I'm repeating myself, but just in case you didn't look at the link. It's not the number of gears, it's the part number.

Redline and Pennzoil Synchromesh are both good for the old Nissan transmissions. Not much better that I've seen written about or tried. There's a lot of buzz about the "Friction-Modified Synchromesh", but if you already have the regular stuff, not really worth spending extra. Use the Synchromesh, I'd say.

What is being flushed? The moving parts are self-cleaning and the non-moving parts aren't affected by "stuff" on them.

I'm not much on electrical but isn't the power of the magnet, the coil, determined by current? Which, of course, is related to voltage. Just pointing out that if you have a relay that's not actuating, and you're reading lower than expected voltage, getting a different relay might not be the "ideal" solution.

You might have a brake fluid leak.

I found an article that shows how MSD's ads are deceptive. They describe set-point timing retarding as "curves". They're not curves. They're just rebranding their rev-limiter technology. Pretty sad, MSD used to be top of the game. https://bangshift.com/general-news/tech-stories/engine-tech-how-a-programmable-ignition-can-make-anyone-look-like-a-pro/

The bushings need to be tight also. If they're destroyed you lose a lot of travel.

Apparently there are three 4 speed shifters also. I used my 1976 4 speed shifter on a 78, 81, and 83 5 speed and never had any problems. http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/transmission-control/4-speed/from-sep-71/27

Looks there are two different 4 speeds, and two different 5 speeds. Parts 5 and 6 respectively. There's overlap. Looks like you got mismatched years, maybe. http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/transmission-control/4-speed/from-sep-71 http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/transmission-control/5-speed

I posted in this thread about using an MSD or Crane module but I don't think that their programmability is very complex. Their ad copy is deceptive. Here is a system that does what I was thinking of. Lots of ways to get spark control, especially in today's programmed world. Somebody has probably developed an app that will let you use a "phone" to run your engine. https://www.cbperformance.com/CB-s-Black-Box-Programmable-Timing-Control-Module-p/2013.htm

The tiniest scratch in the bore will leak. My car had a faint scratch from the wire spring that holds the dust seal in place. The PO must have let it slip and it scratched the bore. It worked fine but let a few drops of fluid leak after each drive. Took me a while to figure out why my tire had fresh liquid on it on a dry day. The PO also put the calipers on the wrong sides. He put the work in but just missed on the results.

You left out 280Z distributor + external ignition module. GM HEI, MSD, Crane, and other modules. Some of them are programmable. The 280Z distributor has the variable reluctor trigger, which is very solid and dependable.

Looks like a Nissan reman. Rebuilt to Nissan specs. Should get 200,000 + miles from it. Do you know where it's been stored, and how? Does it have oil in it or is it empty? I would assume that Nissan coats the internals for rust prevention in preparation for shipping and storage, but who knows how long that lasts. Might be worthwhile to inspect rust prone surfaces before starting it. I don't know when Nissan stopped supplying reman engines but I'll bet it was over 20 years ago, at least. That engine has been floating around for that long. Fixed your picture -