wont go in 3rd plus grinding noise

[rms13Mike]

noticed this earlier today. i can shift to 3rd but when i get to higher rpm it wont go in and it will grind the gear and make that griding/whinning noise. super annoying and scary, i dont want to mess up my transmission. thats the only time it happens, downshifting and low rpm shifting are alright, no problem at all. what could this be? pls help, thanks in advance. i might post a vid tomorrow

[Jdmstyles]

Worn transmission synchros most likely.

Do you feel the shifter being knocked by the transmission when you're shifting?

[rms13Mike]

Worn transmission synchros most likely.

Do you feel the shifter being knocked by the transmission when you're shifting?

what do you mean knocked by the transmission? when i shift to 3rd at high rpm it wont budge in as if i wasnt stepping on the clutch maybe? then i hear the grinding noise, i tried double clutching it it was fine, i was actually think that it might be the sychros too but it shifts fine at low mid rpms, dunno if that matters though