Tranny probablem

Hey i got a 95 gsx when the car is not warmed up it goes in to 3rd gear normal. soon as its warms up it pops out i dont know what it is could you please help thanks.

You need to be more descriptive. What do you mean it "pops out"? Like when driving, or just sitting there? When was the last time you checked the fluid? I suggest switching your tranny fluid to Pennzoil Synchromesh or BG Synchroshift. Going to a higher performance tranny fluid (especially in manuals) usually eliminates or drastically reduces shifting problems, unless you have a bad problem with the synchros, then you're screwed either way.

It Pops out when im driving so i have been doubel clutching and it goes in fine it usally grinds more if im shifting from high rpms from 2nd to 3rd.

Sounds like your synchros might be going bad. I second checking your oil. Make sure you have enough oil in there and i would also second the switch to BG Synchroshift or similar oil and see if that helps your problem if not you might need a rebuild.