Had a similar problem and asked if it was the starter or ring gear three places said the starter. Had it replaced, terrible job took the shop (which does starters all the time) 3 hours to get it out, had to take off motor mount. After the installation was finished, turned the key and it went ZING. Techinican said "Gee must be the ring gear" which is 10 hours labour. Only does it occassionally now so new starter may not solve your problem.
