Screeching isn't a good sign nor normal. When does the screeching occur? Depending on starter type, the aftermarket small starters come with shims to set clearance. You need clearance both away from the flywheel both length and height (proper tooth clearance when engaged). Unfortunatey with top mounts you many time can't get the height right easily. And with stock type starters they usually don't come with shims anyway.
I've seen bellhousings machined slightly wrong too causing never ending starter issues.