If I change from 2nd to 3rd with around 4500 rpms or more i will get a grinding sound from my gears.. its only in the 3rd gear tho.... I can rev my engine and throw it into gear and they all sound fine except 3rd. If i shift at under 4500 rpms i dont ever have that problem... What could this be a sing of and whats cause'n it?

 

sounds like your secrows are gowing out..

 

I would also say the synchros might be damaged. You can try and double clutch and that might be able to stop the grinding, but i'm not exactly sure how to double clutch since i don't drive a manual. Use the search.