Starter whirring, not grinding....
I've gone through 3 starters in as many months, when I turn key to engage starter, there is just a whirring sound, not the usual grinding that is normally heard when a starter goes bad. Flywheel looks fine, no missing or severely worn teeth. Replaced starter solenoid, but not sure what else it could be. When I get the starter the last two times, it starts off fine for the first week, then slowly just wears itself out till I get the whirring sound. Not sure what it could be from. Any help would be greatly appreciated.
1989 Ford Ranger XLT 2.9L V6 "REX"