what goods a large thick ground cable going to the frame going to do to make sure the engine block is able to get the 150-200 amps the starter requires?
that cable is doing nothing as its the cable from the battery to the bellhousing stud (near the starter) that handles the ground side current for the starter.
there's more than a few things it can be, whats voltage drop across the power lead when its clicking? how many miles/starts? (if its started 2-4+ times per day for the last 11 years....yeah starter may be worn tha **** out.....)