Was on the high way driving was going about 90mph and I noticed the shift knob was shaking like crazy and popped out of gear when i was on 6th gear. So i pulled over and noticed that my transmission was leaking as well. So i drove it back home which was like 1 mile away and going no faster than 30mph and in 3rd gear the transmission was fine but as soon as i went to 4th and gave it a little more gas knob vibrated like crazy and looked like it was about to pop out again. And the day before i replaced the master clutch cylinder and the salve cyclinder. Possible problems and before this only 3rd gear would grind in high Rpms but will go in very smooth when wasnt going in high RPM's or when i double clutched.

 

Find out why the transmission is leaking would be a good start. Also check the fluid level.