Occasional Grinding Noise when starting...

[rrossjr]

I noticed an intermittent problem with my '70 GT (Petronix, Otto Start, rest of the start/charge system is stock, Auto Trans) Once every 10 times or so when I turn the key, I get a grinding noise Loud!) with no engine cranking, Usually it starts normally on the second or third try (so far...) Anyway, I didn't see this addressed in the forum, so I'm asking if this is consistent with the starter motor clutch not engaging or incompletely engaging, and why it is is intermittent (so far...) Is there anything I should look for, before shoving in a new starter motor (which I actually have sitting on a shelf)
Thanks,
Ron in Indy

[Jeff Pozorski]

The large ring gear which is engaged by the starter drive is missing a few teeth. You hear the sound when the starter drive trys to spin the gear and comes upon a missing tooth, allowing the starter to spin freely while also nicking the next tooth in line. My Manta, automatic, also does the same thing on occasion. Nothing harmful but damn irritating when it happens.

[baz]

as jeff says it sounds like a problem with the starter ring
may be a good idea to pop the starter off and turn the engine over by hand (spark plugs out would help this ) and look for missing teeth / worn down areas on the ring and have a look at the worm on the starter too

[rrossjr]

Thanks Jeff and Baz,
I'll take a good look at the teeth on the ring gear (Maybe do a little flossing ) Seems like it's not getting worse, but as Jeff says, very annoying.
Ron in Indy

[GTJIM]

Make sure the starter mounting bolts are tight - loose ones allow the starter to move around which makes it all worse....

[opelwasp]

It will get worse over time reguardless. You need a new flex plate, not used, new. Good luck. Been there done that.

[rrossjr]

Originally Posted by opelwasp It will get worse over time reguardless. You need a new flex plate, not used, new. Good luck. Been there done that.

So, Chris, where did you find one?
Ron in Indy

[jerseyopel]

You cant find a new one. You will Have to find a good one in a junkyard or pull the ring gear you have, Grind the few welding tacks down that hold gear in place and flip it over and retack it.

[opelwasp]

Some one may have an NOS one stashed around. You may also be able to get the old ring gear removed from your flex plate and have a new ring gear welded on, I would have it done at a machine shop. And I never got around to replacing mine. I ended up selling the car, now owned by Jonzo.