would def still say it would be related to the clutch arm,as if it was not there before and now is which what hapened to me as well,if you take the box out should have scoring on front face of clutch pressure plate from whee it touches btw will eventually kill gearbox as the stiffness is caused because clutch is not disengaging properly and could stop diengaging at any tie if release arm snaps then ould have to be flat bedded home/garage for repair.