i have a 1975 280z 2+2.

The issue I'm having is that i cant shift into any gears while the car is on, but if the car is off i can shift in to gear easily, I've already replaced the master and slave cylinders.
I'm at a complete loss to why it wont shift gears there is only 18,000 miles on the car i don't believe the actual transmission is bad since it just randomly happen while i was driving i had stopped at a light and after that i couldn't go back into gear.
also if i leave it in first gear and turn on the car while the clutch is being pressed the car still wants to go forward,i assume this is related to the issue.

Any help would be appreciated.

 

Welcome to ZDriver!

Did you bleed the system?
When you push in the clutch pedal, can you see the fork moving on the side of the transmission?

 

I did bleed the system, how do i see the fork?

 

Well the easiest way is to have a friend push the pedal in while you're under there looking... or just use your arm while looking under. The fork is attached to the end of the slave cylinder.

 

is this what youre talking about

 

That is the fork yes. When you push the pedal, see if everything actuates. Could be a few things gone south, but it will be troubleshooting that gets you the solution, as there is a few moving parts there that could potentially cause the pressure plate not to disengage.

 

would that require me to take apart the transmission?
that little pin moves and so does the thing its hitting

 

How does the pedal feel, does it have feedback, like you can feel the pressure plate pushing back on your foot? How much does the pin and fork travel?
When you wiggle the fork, does it feel loose? If the system is bled good and you are getting full travel, then it will be something more, which will require to pull the trans. Could be broken pressure plate fingers, fork damaged, pivot ball damaged..etc. If you heard anything strange before it stopped shifting fine, then most likely internal issue.