Best bet is you can try to heat the cup and it will melt the locktite, but you need to be careful you do not heat it too much and damage any of the trans parts or bearing, then you can try using a standard size allen key instead of a metric one, Or last resort is to drill the set screw and replace the drive cup. What car is the 2 speed on and is it just the normal cup or is it the brake disc cup?