The dead spots on the flywheel are actually places where the ring gear teeth are beat down and the starter gear doesn't engage them.

So - the solenoid engages, whams the gear into the ring gear. That movement also connects that fat red cable from the battery to the starter motor - many amps for lots of power.

the engine starte, the flywheel spins faster than the starter gear, and the mechanism releases so the starter gear is pulled back into its housing.

What if the starter gear engages nothing? What's to trigger the retraction mechanism? Nothing - it just keeps spinning.

Keep the old starter. Check the flywheel ring gear. PITA but that's it. If you have Manual transmission, put car in 4th and push a few inches. The ring gear will move and maybe the spot on it will have good teeth.

If you have automatic trans - it will have to be dropped to fix the ring gear. Well, OK. While you're in there you will porbably want to replace the rear main seal, the transmission mount and any other wear parts in sight.

Good Luck,

Bob

:>)