Outer Limits 4x4 Board

hey guys i got LWb mq and over the past week i am having problems getting it into 4th gear with out a grinding of gears..

Could this be clutch or box problems.. or something else i dont know about

Cheers

im no expert on gearboxes, but i think it could be a "lazy syncro" ie the syncromesh isnt lining up properly...........