My first gear loves to grind when i push in the clutch real fast and try to put it in first. The weird thing is, if i push in the clutch and leave it in for like 5 seconds it will go into first gear no problem without a grind (keep in mind i am completely stopped during this). I have a brand new slave cylinder. I am just wondering if this problem could be the synchros or the master cylinder. It will only do it in first gear. I am 100% sure the clutch is bled right and that its not the problem. Also am i worth buying a used tranny or rebuilding the one i have if it is the synchros?

could anyone tell me?