I've got a 93 mustang 5.0 LX with a starter problem I just can't seem to lick. The starter starts the motor with no trouble. The problem is that when the motor fires, the starter wants to drag for a few seconds and then it will release from the ring gear. I've tried several different starters...new and reman, I've changed out the solonoid twice, replaced the ignition switch, shimmed the starter, put a new ring gear on the flywheel. I'm out of ideas. The car was fine when I bought it, and then one day it just started doing this and I could never get it to stop.
I've held the starter in my hand and had my wife turn the key and the starter drive seems to not retract as soon as the key is released, but the drive does stop turning immediately. I'd say it was the starter motor, but I've tried at least 5 different ones and it's always the same thing. Everything appears to be lined up properly. Any help would be appreciated.

Sounds like a electrical problem to me. To take a quick check, I would put a multi meter on the solinoid input and see if the power is still there when you start it. Don't know the full electrical system on these, but could there be a relay that could be staying open a little to long? Without a repair manual I couldn't tell you for sure. I have a Chilton at home, but only goes up to 91, but will try and look in it to give me an idear tonight.

Just a thought, but it could possibly be something in your ignition sticking for a moment when you turn your key back that is allowing power to your starter for a short time.