240sx transmission problem...

long story short was driving today then boom, sounds like there's a can, rocks, or just like metal grinding in the transmission. its still mobile, but is my transmission trash?? (5-speed btw)    

Have it overhauled. I'm guessing you never had it serviced.  

Probably lost a bearing in there. Most likely not a good thing. If it was a throw out bearing it would make a different sound and is completely repairable. Internal sounds like that means some thing detonated and needs to be replaced. With luck, it may be some thing that can be fixed, but it means taking it out, tearing it down and inspecting it. It's unlikely, though. Sorry.
 
How you drive is your buisness. Remember that you're not the only one on the road!
Educate, don't hate.

well i swapped the transmission, and it still makes that noise, it couldnt be the engine couldnt because it only makes noises when its in gear or on neutral. but once i step on the clutch it goes away cant be the engine has a fresh rebuild... could it be a loose flywheel?? or something loose on the clutch??  

Did you use the same throw out bearing that was in the one you swapped out? If so thatcould bve your problem. The chance of having two transmissions with the same problem and it goes away with the clutch depressed is huge. It's got to be the throw out bearing, assuming that you used it on the swpped in unit. Advice, never use used parts even if they look good or haven't given you problems. Some times the cost of some thing small, like that bearing, far out weighs the trouble of removing the trans a second time to replace it. Cool? Once you've gotten in there to see if any thing is loose, replace the throw out bearing any way. Have the pedal adjusted when you finish doing all that. There is an adjustment at the pedal that keeps the throw out bearing from continuosly touching the spring plate. This constant touch wears the throw out bearing right out. At the top of the pedals sitting postion you should have any where from half an inch to an inch of free play before the pedal feels like it's giving pressure to the clutch. The other feel you should have is that when releasing the pedal to make it go, the clutch should grab when the pedal just about reaches half way before it reaches the top of its travel. It would actually be almost one third of the travel  when releasing the pedal to make the car move. You have some lee way, give or take a half inch. Any way, let me know if I was any  help with that diag.
Good call on the engine not being the source of the noise. If it was the engine, you would have a completely different noise and really bad noises that would actually leave you walking... or blow a rod through the engine wall. I hope I'm right about the throw out bearing. Good luck.
 
How you drive is your buisness. Remember that you're not the only one on the road!
Educate, don't hate.