Hi all I have a transit 260 51 plate swb grinds or crunches in second?

Hi all have transit 260 swb 51plate all gears work fine apart from second must times it crunches some times grinds but now and a gain if driving slow it gos in fine really need sume advice would this b the gear sellector cables or the sellector where u all say bout the bolts it's really stressing me out help would b call chers