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Slightly chewed ring gear?

3563 Views 12 Replies 6 Participants Last post by  DragonProof
I just picked up a '73 ford 3550 that wouldn't start. Got her home and pulled the starter and found she had a relatively new starter and a slightly (?) chewed up gear ring. I know the usual advice is to split her and replace the gear ring, but I'm thinking this one is not that bad.

Full disclosure: the only time I've ever repaired a gear ring is when I threw out the flywheel in my M551 Sheridan tank, which coincidentally was also a '70's era machine. So I have no idea if the 3550's gear ring is still serviceable.

Ive attached some photos of the gear ring and starter motor. If you look at the gear ring it looks like the starter motor is failing to engage fully into the gear ring. I'm wondering if the burrs on the gears are causing the bendix gear to kick back and fail to fully engage? Maybe I could file down the gear ring? Or is the bendix gear spins up too high while trying to fully engage?

I bench tested the starter and saw that the bendix gear does fully deploy.

I wonder if there is a different style of starter motor that will throw the bendix gear to it's fully extended position before applying power to the motor? Seems like this should allow the gears to fully mesh before the starter starts spinning up.

Anyhow, any advice will be greatly appreciated.

Guy in Olympia


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I would dress the gears on both flywheel ring gear and starter. When the solenoid pulls the gears into mesh, the power to the motor is the last thing applied. It should not be spinning when trying to engage. I would check the adjustment on the solenoid contacts using a meter to find at which point in the 'stroke' the juice will be applied to the starter, and if way before engagement, I think you'll have found the problem.
The nose(?) of each gear should be shaped to tend to encourage the teeth to slide past each other when the solenoid gives them a kick. Once past, then wham with the juice.
I think a Dremel type tool & abrasive bit can make them work pretty well. I have seen some really burred teeth on the ring gear, and the starter still worked.
If you can find an ring gear like yours and use that as a guide to shaping the edges of the teeth I think you'll do all right.
Worth a try rather than 'building a gantry...' and all that follows, I think.
Personally, I would not worry too much about the minute amount of filings you'd produce dressing the teeth. If desired, you could use a magnet or two near the teeth as you work on them, moving them as you work your way around the gear. I suspect the turning of the clutch and flywheel would create a bit of a whirl inside, and any particles would tend to be flung outward towards the inner surface of the clutch housing rather than into the clutch mechanism or between the flywheel/clutch/pressure plate. But sometimes I am an optimist, so other opinions may be posted.
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