so when i'm driving in 3rd at low speed it just drops out of gear into netural it never grinds or miss shifts which is why this is odd never a problem until saterday night i pull out and rip from 1st to 2nd and when i try to go to 3rd its stuck in 2nd and so i had to push it out and then it wouldnt go into any gear it check the clutch fluid its black so i flush it out and the clutch and tranny work fine except for the weird 3rd gear thing

 

I've had this issue happen before. Chances are you have wear on the 3-4 shift fork pads and the fork is not pushing the slider over the 3rd gear completely.