How to stop grinding sound when changing from 1st to 2nd gear near redline

[Tweak]

Hey all. I own a 99 hyundai excel twin cam and recently (within the last 2 months) i've noticed when i change gears from 1st to 2nd really fast near redline, it makes a grinding sound as if the clutch wasnt fully depressed. If i stomp it down that seems to do the job but that needs a really big stomp and its hard to do when moving that fast. I thought buying a short shifter would fix it as i read it would but after its installation i noticed that it only shortens the length of time the gears grind for from a second long grind to something like a half second grind, which is better i guess. I read on the forums that changing the gear oil would be good and since my car has done round 75K km's i got a shop to doit but i forgot to specify to put in redline gear oil and they put in valvoline synthetic which i've noticed little to no change sofar... I really wanna get rid of this sound as it's stopping me from driving as hard as i did...(when the gear oil was changed, no teeth were found so my gearbox is fine i think) what would fix my problem? I read that changing the gearstick linkage might doit, are these the cables attached to the gearstick? how do i change them to fix my problem? Could it be that the clutch isnt fully disengaging? could it have an air bubble in it? would bleeding the fluid and replacing it possibly make the clutch fully disengage, eliminating my problem? my last option, if this would really help, is to change the oil "again" <sighs> but i want to consider my options before doing this and i think it might lie within changing the linkage. does anyone have any suggestions?