rattling grinding type noise at highway speeds

[cometcougar]

Hi all. I'm experiencing a new problem with my 60 Comet, and thought I'd try running it by all of you to see if it sounds like something you've encountered before. Yesterday, at freeway speeds, I hear a pretty loud gear grinding/rattling type of noise. When slowing down below 45-40 or so it would stop, but then come right back again. I was thinking it might be the 2-speed auto trans, but now I'm not so sure. I played around in the driveway, and it seems like it is making the noise in the flywheel (or I think it is called a flexplate with an auto trans) area. Then I got to thinking that the noise sounded similar to that horrible sound when you try "start" an already running car. Now I'm thinking, perhaps it could be the little gear on the starter is for some reason moving into and contacting the teeth on the flywheel. Could that happen? I think I'll pull the starter tomorrow and see what I can see with that. I was going to do it today, but it was so darned hot down there with the exhaust after messing around with the engine running and troubleshooting, and by the time it cooled down enough to work on, it's too dark outside to see what the heck I'm doing without running a bunch of electric lights. Sooo, (sorry I'm long winded tonight, I guess), if this sounds at all like anything any of you might have experienced, I'm open to any and all suggestions as to where I should look to solve this problem. Oh, and one more thing that got me to thinking it is not the transmission is that the fluid is clean and red (type F), and no burnt smell to it at all. Thanks for any and all advice!

[Luva65wagon]

Ford starters have a return spring to pull the bendix (the part with the gear) out of the ring gear when the key is released. If you start and still have the key on for a moment it (the bendix) also has a reversing action to force the gear back as well. But if the return spring (it's actually lifting a fulcrum that pulls the gear back) is broken, then the gear would float around and into the ring gear on the flex plate. Can't say I've ever seen anything like this, but it would be obvious when you pull the starter. If you can easily slide that gear in and out of the starter, pull that cover off the side and the spring is under that. If is is this, I don't know why it wouldn't do it all the time rather than hiway speed.

[cometcougar]

Well, I got a chance to remove the bottom inspection shield off of the transmission and removed the starter today. Starter looks to be just fine. Found where the area around one bolt around the perimeter of the flex plate is cracked, and the ends of some of them look to be cutting a deep groove into starter - evidence of fresh metal particles there, and the arc they are grinding through the starter looks clean and fresh. Cracked flexplate would seem to be my culprit? At higher speeds the cracks are allowing the flex plate to, well, flex too much? (Any advice is much appreciated!) Is this something I'll be able to get new at an auto parts store, or would you suggest I look elsewhere (and if so, where?)? Thanks all.