Starter problems?????

[dj_joker_2002]

First things first! Iam on my 4th astro/safari - this is the 3rd with V8.
Anyway I bought a brand new starter for the 3rd van and it was used for maybe 5 months then I blew the engine (due to overheating) I removed the starter and set it in my barn on a shelf.
It sat there for about a year, then I put it on my new engine (V8)in my 4th van. I had no problems with it except once in a while it made a loud screech type noise once in a while when turning over the engine. SO I put a shim on the starter and then a new problem arrose. now it makes a louder screeching noise but does not turn the engine. SO I tried again without the shim and its loud and no turning of the engine. Anyone have any idea whats happening here? do I need a new starter again? ](*,)