Magna TF unique starter motor isuse.

My car suddenly started to make a terrifying loud noise. It literally sounded like a bucket of bolts being shaken around in a tin can. The car started, and drove fine...I could not pinpoint the exact source of the noise. It was just "somewhere inside the engine". Terrifying.

I bumbled into suggestions online implying a broken flexplate/driveplate (flywheel on manual transmission cars). I listened to some youtube videos online of this problem, but the sound wasn't quite right. In some obscure forum comment somewhere while looking deeper into the flexplate issue, I saw a guy mention the starter motor failing to disengage properly as a cause for some really crazy noise. While closely related, this is different to the sound you hear when you leave the key turned too long when the car has started. In that scenario, the electric motor is under power.

...so, given the complexity of dealing with an auto-trans on an East/West front wheel drive...I decided to investigate the starter motor first...

Here you can see the pinion gear doesn't really look retracted very much. It doesn't match photos of a new starter motor.

Two long bolts hold the motor to a planetary gear reduction and the pinion assembly.

The planetary gear is housed in a plastic casing. You can see this collar has broken off.

I determined that the plastic collar only serves to retain the planetary assembly as one "part" before the entire thing is assembled together with the Y-harness/spring for the pinion, and the electric motor. Once the electric motor rotor is aligned inside the planetary gear, the plastic does nothing. Everything is retained and aligned by metal parts after that. These broken parts rattling around were interfering with the intended stroke of the pinion gear.

Reassembled. Now the pinion gear looks retracted correctly!

So back in the car...everything works great! Problem solved.