It's just stiff and difficult to engage - no crunching. Looking at the gear shift mount within the cab, it looks like it has an inspection plate on the side which may double up as a greasepoint or something. I'll have to borrow a spanner (imperial) and have a look.What is the air filter like, does it look dirty? If in any doubt replace the element and turn the tick over up slightly and see how it goes.
Is it stiff selecting the gears or does it crunch as you try and change down? If it's just stiff then the linkage may need a slight adjustment