As above, the first things to check.
If alls ok there, try oiling the input shaft uj's , they get sticky and notchy.
If it gets better after the oiling but still not right, oil some more and/or replace them.
Mine wet stiff suddenly another landy man at the sailing club immediately said UJs a quick spray of wd40 ( all I had at the time) cleared the problem. Later I used grease and rubbed it into the joints properly. Never had a problem since.