It might be that the 3rd piece is doing all of the work.  Be careful.  Do those two pieces have jagged edges like they broke off of something?  I recognize the tooth pattern but can't tell where it would have come from.

Examine a bit closer, the 2 pieces might me just 1 of the 3 pieces.  It should look like this.

 

 

I've been scouting the internet and seem like this part is no longer available.  Need a donor.

The broken part look like #5.  Synchronizer hub

From Dave WM. Second post 

 

Edited April 7, 20222 yr by 240zadmire

Well, I pull it off last night…

all the gears seem to be in good condition.  No chip or damage to the gears.  As suspected , the synchronizer hub is destroyed.  More debris found in the casing
 

been searching for replacement part but seem like if any available, it will be from a donor.  Any one has spare and is selling, please let me know.  Also, will the 4 speed work ?

The 5 speed is basically the 4 speed with an extra gear engineered on.  The parts should be interchangeable.  You can tell by finding the part number on the carpartsmanual site and comparing diagrams.

@Terrapin Z has a large collection of parts.  You might want to disassemble further though to see what all you need.

 

Looks like the 4 speed uses the same part.

http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/transmission-gears/5-speed/44

http://www.carpartsmanual.com/datsun/Z-1969-1978/power-train/transmission-gears/4-speed/from-sep-71/27

Ouch. Main shaft hub exploded in the 4th gear section of the hub. Don't see that happen much.

The main shaft in front of the adapter plate in the 4 speed and 5 speed use the same parts. You should be able to find a hub easy enough. I'm very sure the early FS5W71C uses the same hubs on 1&2 en 3&4 positions. Early meaning the FS5W71C with the 16mm gears.

Are those chips in the front counter shaft gear/input shaft? The photo blurs a lot when I zoom in.

Yep, ouch is understatement 😉 

 

it cleanly exploded toward the front engine.  The giant bearing has some play as well as the bottom bearing.

 

look like I’ll have to create a gear puller as those gears  are quite deep.

finding a replacement parts are the pain as well.
 Have anyone use jp-car parts.com?  Seem like they have some used ones for sale

 

I'm sorry to see the carnage, and I hope you get it fixed up.

And I don't have anything technical to add, but just gotta say... Wow. I'm impressed. That's not the kind of thing you see everyday!   

And it still ran!!!

Thanks gentlemen.  It happened when I was 17 miles away from home.  Thanks God I was able to get home without riding on top of a tow truck.

the hunt for the parts begin!
 

will keep the thread updated in my quest 

 

regards

 

Before you start hunting parts, can you tell what the marks on the front gears are? I can't get a clear view in the two  photos marked in red circle.

if the input shaft and front counter shaft gear are damaged, it might be cheaper to source a 5 speed and fit a bearing kit. And I'm saying "Might be!!!" These transmision and parts are getting harder to find so you will need to know what you ned first and then check your options.

 

The hub broke very clean. My best geuss is it happened when you went from forth back to third. The damage was done when you was in forth, but the pieces stayed in place until the gear sleeve slid over to third. It's an interesting failure, one I have not yet seen in person.

And now why did the hub go through so much stress? It could be a worn neddle bearing between the input and main shafts causing mis-alignment between the shafts. It would be interesting to see how much wear on the needle bearing and surfaces.

Edited April 9, 20222 yr by EuroDat