[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

 

[dave_r]

So, when it was assembled, and you tried to start it, what happened? Did the starter go at a high speed, and sound like it ground on that flywheel a bit, but the engine didn't turn over at all (or just a little)?

 

[DragonProof]

Yes, that is exactly what happened. There is a slight grind, The motor turns just a fraction ( you can see the generator move like 1/16 inch), then the starter motor just whines like it is spinning at high speed.

Occasionally it will catch and start. When it does there is no grinding noise and it starts like a brand new tractor. I’m thinking there is maybe one good tooth that finally moves into place and allows it to catch.

 

[Michigan Brian]

sorry but 30 years of being a mechanic tells me that flywheel is toast

 

[DragonProof]

I agree the ring gear is toast, but I wonder if there is some way to keep it in service until I have the time to fix it or replace it. There is enough tooth left on the gear ring so that once the pinion engages it is a solid crank.

Here is one hack that I tried: I removed the solenoid cover and reinstalled the starter. Then I held the solenoid in the activated position with a wood dowel while I cranked the engine. It cranked over just fine but I didn't let it start. I tried several more times and it cranked solid almost every time. Occasionally it would do the grind and whine thing ... but after the starter slows down enough the pinion makes a loud clunk and slides into place, so on the next attempt it cranks just fine.

Not sure if this tells you anything. It makes me think there must be some way to recalibrate the starter motor and solenoid to match the wear on the ring gear.

Or if there was some way to modify the starter motor so it would not spin up until the pinion was fully extended.

A new ring gear is about $30. Getting to it is an entirely different story. The instructions that I found started with "build a gantry".

 

[rayjay]

I would look at a new or good used ring gear and then try to grind this one to match. Doesn't have to be your exact one, just any undamaged ring gear. Also make sure the pinion gear teeth on the starter are not already buggered up.

 

[dave_r]

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.

You could also try just cleaning & lubing the starter drive gear mechanism, as it may not move freely enough for the solenoid to reliably move it into place.

 

[Newsman]

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

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

 

[tomw0]

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.
tom

 

[DragonProof]

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

 

[tomw0]

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.
tom

 

[Newsman]

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

 

[DragonProof]

I'll get some photos and post an update. I ordered a new starter, they sent the wrong one so I had to send it back for an exchange. Took a couple of weeks, got the starter back but due recent snowstorms here in the PNW I have not had a chance to install and test it yet. If only I had a tractor to plow the knee-deep snow off my access road.