I have a 93' SE 5speed and I cant put it in gear when the car is on but when the car is off i can put it in gear. When the car is on, if i fight it i can get it in gear but it makes a noise which i dont think is good. I replaced the clutch master cylinder and the slave cylinder and it still does it. I think it might be in my transmission but not sure. Just want to know if anyone has any suggestions??

 

the same thing happens to me but not all the time, most of the time it happens before the car is warm but what i do disengage the clutch and try it again, usually it works on the 2nd try, if yours doesn't work all the time its probably due to totally worn synromesh, which means you have to replace the synronizers, a new clutch wouldn't help, im probably going to be down the same road in 6 months or so, nissan trannys blow PEACE

 

Wild shot in the dark time: are you sure the clutch is disengaging? I may be a little fuzzy on transmission operation, but I think that if you disengage the clutch with the car running, the transmission parts should stop spinning after a while and stop, then it should be as easy to put into gear as when the car is off. Have you tried waiting a while with the pedal in before putting it in gear? If this works, then I would also think that it might be bad synchros. But if this doesn't work, no matter how long you wait, then I'd be inclined to think the clutch really isn't disengaging. If you're sure the clutch hydraulic system is working properly and has no air in it, maybe you have a worn out clutch diaphragm spring? Or maybe broken parts connecting it to the pressure plate? Again, this is a (hopefully) semi-educated guess. Look into this, or if all else fails, ask a transmission shop.

btw, that noise that it makes when you force it into gear is most likely clashing gears so yes, it's a very bad noise. Could occur with bad synchros or if the clutch isn't disengaging. I'd be inclined to have the transmission oil changed once you fix it too, just in case you managed to grind up some metal shavings inside. Good luck.

 

Did you bleed the clutch lines from both bleeders? On mine, there's a second bleeder which is located on the driver's side strut tower. It's not mentioned in the FSM, and it has to be bled AFTER the one on the slave cyl (per the 4th gen FSM). I also replaced both master and slave cyls, and I still sometimes have trouble going into 1st gear at a light. Otherwise, tranny works fine, so I'll live with it for now...

 

What are the synchros and where are they located?

 

Synchros are short for either "synchronizers" or "synchromesh" (which I think is actually a GM word?) They're things inside the tranny that let you shift gears smoothly by making the gears spin the same speed, so they're synchronized. In the old days manual trannies didn't have this and you had to double clutch to shift gears and do the synchronizing yourself - there's a reason they're nicknamed "crashboxes".
You can't really inspect or replace them yourself unless you're a transmission whiz, only can tell if they work yes or no. Not for the faint of heart (including me)

 

maybe

 

already checked gear oil and its ok!

 

how much to replace/fix synchros. If I take the trans. off and take it to a shop how much and how much if i let them take it off. Ive taket the trans. off before so i know how to do it but its a pain in the ***.