I resently rebuilt this 91 nissan maxima Se 5-speed and installed aftermarket sachs ceramic puck clutch and now it's all broke in 4000 miles later my tranny won't shift if I don't rev macth it but sometimes the clutch will work perfect agein and it will allow me to shift normally but only for like one shift then its back to the clutch peddle sticking and my gear box getting grinding when I shift! Also when I engage my clutch just for a second I hear like a metal on metal wine so I checked my clutch fluid an it was blackish so I parked it yesterday but I have no idea what could be wrong because this is my first mannal I don't know much of anything about them): so any help would be greatly thanked.

 

Have you checked your clutch fluid? I wonder if you've not got a bad/leaking master or slave cylinder. A bad slave cylinder would definately contribute to the engagement and sshifting issues you describe.

 

That's part of his problem but I think that his shifting at speed being tough/grinding/needing to be rev matched is a syncro problem.

92maximadriver92 you said you recently rebuilt the transmission, are you SURE you used a GL-4 and NOT GL-5 fluid? GL-5 fluid does NOT supersede GL-4, it will eat the soft gold metals inside our transmissions (specifically the brass syncros) and cause shifting problems.
When you did the transmission or clutch work did you replace the master/slave cylinders for the clutch? If you haven't replaced them you should make sure they aren't leaking and bleed the system properly (you might need to look up a walk through and/or ask questions here)
When done properly, you will have no dirty fluid anywhere in the system.