Did I just break my AZ6? Locked out of gears 3-4-6...
 

I have previously broken one AZ6 I blew the teeth off 4th gear, but the trans would still go into every gear and i actually drove it for a little while like that just skipping 4th gear. We all know 4th is the weak link in the az6. Today I was driving on the highway I did a 3rd-4th-5th pull getting onto the highway and shifted to 6th no problem at all no odd noises. Went to get off the highway and when I came to a stop the car would literally not go into any gears at all. I eventually forced it into 4th gear and limped it home. Even with the car off the trans does not want to shift. I took the shifter off and everything looks ok there. I was actually able to get it to go into 1st-2nd-5th and Reverse smoothly. Gears 3-4-6 I cannot get no matter how hard I try to force it. My hydraulics are all working correctly so my thought is that maybe I bent a shifter fork internally or a synchro desenegrated....I honestly have no idea. My clutch is old its a SM 4 puck sprung and its been in the car for 4 years with zero issues. My car makes 370+ftlb so if this thing is broken I wouldnt be surprised. I still have my other 6 speed I thought about taking both apart and making one good trans with the spare parts. Has anyone had this issue and can shed some light on what might have happend? Thanks

Edit : I just started the car in neutral and tried to select some gears and its really odd, the car will feel like its in neutral but itll still be engaged like its in gear. The shifter sometimes will get stuck, and it has SO MUCH resistance and its hard to even find neutral again. It feels like something is jammed up or broken, but I dont think there is any damage to the actual gears themselves bc it doesnt make bad noises I just cant select gears with any ease whatsoever.

Shot in the dark, but a journal bearing exiting a shift fork or pivot can lock out oddly specific gears.
It's all guesses without splitting the case.

Yea most likely I'm gonna buy another az6 then split this one and my old one apart and attempt to make a good back up trans from the two broken ones. Should be a good learning experience. I have rebuilt a lot of Nissan autos in my time there but never a manual trans

My bet is something broken in the shift rod system or failure of the bearing between the input and output shaft.

I've done a bunch of manuals and a handful of autos. I prefer manuals by a huge margin. Far easier IMO.

I haven't done an AZ6 yet...

You will like rebuilding manuals.

Interested to see what you find.

Well, went out the the car the other day and forced the shifter into 3rd gear. It did not want to go but I literally forced it in, after that all the sudden it shifts fine and makes no funny noises. It's like maybe some foreign material was stuck internally.... Who knows. I'm gonna drain the fluid and look for particles but so far it works perfectly again and shifts great. I have no idea what could have caused this in the first place.

Something broken/bent in the shift rod system wins...
Take turret off first to inspect. Look at fluid.
Personally, I'd pull the puppy down to figure out what happened.
Might be inexpensive to fix now...
There are little detent balls, plungers, and springs between the individual shift rods (keeps you from selecting two gears at once) and I'd expect the problems to be there.

Had a really bad shifting 6-speed when an IRP shifter (never buy these btw) started to fail, not sure what your shift setup is, but worth a shot. This issue locked the trans out of 6th and reverse.