Slightly chewed ring gear?

3569 Views 12 Replies 6 Participants Last post by DragonProof, Feb 19, 2019

DragonProof

Discussion Starter · Jan 18, 2019

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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· #8 · Jan 19, 2019

DragonProof said:
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 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.
Guy in Olympia

dave_r said:
I would first measure how deep the flywheel gear is from the mounting surface, and compare it with the starter. Maybe somebody put the wrong starter on it, so it just barely catches the edge of the flywheel when extended, instead of being centered on it.

I would agree with Dave, and since it is relatively new, check the number. Just a WAG (WildAssGuess) but there is an outer gear diameter variance on many of the 10 tooth CW starters for Ford Tractors, albeit, not the correct one but will still bolt up and work, for a bit.. For some the diameter is 1.264" while others are 1.575". The correct one is the smaller gear, which would allow it to fully engage the ring. IF the wrong starter, i.e. 1.575" gear was used it would only engage with the end of the gear teeth. It is also possible that there are unneeded shims used when mounting the starter which would have somewhat the same effect. And sorry to say, but yes should replace the ring gear. Just my 2¢.
MikeC

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Newsman

· #12 · Feb 18, 2019

DragonProof said:
Thanks folks, to everyone that replied. Lots of good ideas here! I'll start the process of dressing the gears, making sure I have the right starter motor, measuring and testing tolerances, etc. As I complete each step I will update this thread.

One question / concern: as I am dressing the ring gear teeth there will be some metal shavings falling into the housing (along with the metal from the already chewed teeth). How much of a problem is this? Maybe I can get a magnet down to the bottom of the housing, or flush the housing somehow. I'm guessing that the clutch is in the same housing, I don't want to cause damage to that.

- Guy in Olympia

Just cking in to see if any progress on this.
MikeC

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Slightly chewed ring gear?

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