Ford 6.7L Powerstroke Ring Gear teeth worn/chipping

Timothy Owner/Technician Metter, Georgia Posted   Latest   Edited  
Unsolved
Drivetrain
Parts
2011 Ford F-250 Super Duty FX4 6.7L 6-spd (Selectshift)
Starter Sometimes Grinds Without Engaging Into Ring Gear
Ring Gear Teeth Damaged At Places On Ring Gear Where Engine Normally Stops When Shutting Down

Hello Sirs, 

I have a repeat ring gear failure on this truck. At 60,000 miles on 10/2017 this truck showed up with the complaint of the starter not always engaging properly. It would grind for a bit and then catch and start. Sometimes it took a few tries at cranking until it would finally catch and start. We removed the starter and inspected the ring gear and found the ring gear teeth worn down and at least one tooth was broken. Here are two pictures showing how the front edges of the teeth had been flattened off and also showing the broken tooth.

Ring Gear 2017

Ring Gear broken tooth 2017

We ended up installing an OEM Ford flexplate/ring gear and a new Motorcraft starter even though the starter teeth did not appear damaged. We replaced the starter in hopes that the starter had not been throwing the drive gear out well enough and causing the ring gear to be damaged.

It worked well until recently at 80,000 miles it returned again with the same grinding symptoms intermittently while cranking. We removed the starter and found the ring gear damaged very similar to before. I believe we found 4 worn spots on the ring gear since this V8 usually stops at one of four areas on the ring gear ( If I am correct on that ). There we two spots worn worse than the other two. See pictures below of this time around. This engine runs perfectly and has no engine mechanical or electrical issues. The truck is in good condition and the batteries are good as well. The starter drive teeth also appear to be in fine shape this time as well.

Ring Gear 2019

Ring Gear Teeth 2019

What could be causing this to happen? The first time it happened the broken tooth was near a weld spot on the ring gear and we thought maybe the welding process hardened that specific area. But there are other worn areas that are not near/beside a weld. Do we need to try a performance flex plate/ring gear like the Billet Suncoast. The owner does not put a lot of miles on per year and usually runs it locally so it probably gets quite a few cranking events during its operation.

I'd be glad to hear any options you know of to remedy this. 

Regards, Timothy

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Matthew Technician
Hastings, Michigan
Matthew Default
 

Any mods or peogrammers installed on this vehicle?

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David Owner
Metter, Georgia
David Default
 

This truck is completely stock.

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James Owner/Technician
Santa Barbara, California
James Default
 

Was the starter at 60,000 the original or had it been replaced previously? Reason I ask, sometimes it only a difference of 1 tooth. Some starter applications use 9 e teeth others are 10. Only difference may be between stick and automatic trans. Verify by truck application, not starter number since it has been replaced at least once before. i got bit by this in the past.

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Timothy Owner/Technician
Metter, Georgia
Timothy Default
 

As far as I know it was the original starter at 60,000.

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George Owner/Technician
Mobile, Alabama
George Default
   

Looking at pic #1 I would say the pinion is not going deep enough (verticle) too much clearance in the working depth in the flywheel. The tooth pattern looks as if the pinion diameter is too small. I am assuming that the starter boss fits snug and no sloppy movement allowing the starter to use the bolts for aligment Should be a 12 tooth drive according to my info ,,,Diameter 1.427 in. Since…

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Timothy Owner/Technician
Metter, Georgia
Timothy Default
 

This is not a rebuilt starter. The first one was the original starter that came with the truck from factory. The one we installed was a new OEM Motorcraft PN SA1004 which is superceding to the PN of SA1142. This starter does have 12 teeth. The tips of the teeth on the ring gear and the starter gear do have a chamfer. My thought was maybe the ring gear teeth do not have enough of a chamfer.

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Karl Educator
Milford, Nebraska
Karl Default
 

Just for kicks, are you getting good battery voltage and ground at the starter? Is the starter mounting surface parallel to the transmission mounting surface?

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John Instructor
Beaver, Pennsylvania
John Default
 

One of my first thoughts when I see a ring gear fail like this is how much end play does the crankshaft have? I haven't seen enough power strokes to know if they have much of a problem with thrust bearing wear but it is something that I have seen a number of times through the years on other engines.

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Glen Owner/Technician
Arthur, Illinois
Glen Default
 

Can you post the VIN? That rubber cover pinched in the adapter plate, would that be enough the mis-position the starter? Do you happen if the balance marks on the TC and flywheel where lined up? What about doing a RC test with a scope or IDS? Does it have remote starter? Do you remember if the dowel was in the crank and were the flywheel bolts replaced?

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Timothy Owner/Technician
Metter, Georgia
Timothy Default
 

Thanks Glen. All very good thoughts. The vin is 1FT8W3BT3BEB47557 We did replace the flywheel bolts with new Ford Bolts. Doesn't have remote start that I can remember. Customer has taken truck again until we get a resolution. I dont remember about the dowel pin or the T/C and flywheel lineup. I was not the one that did the work in 2017 but we are the only shop that works on this truck and it…

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Glen Owner/Technician
Arthur, Illinois
Glen Default
   

The posted part # match what I see in the catalog. As for the balance marks it's hit or miss in SI and I am not sure how much difference it makes. I will try to get some model specific that list it in SI later tonight. I looked in the WSM it mentions the marks in the trans and engine installation. The WSM may make it a little clearer on a '19. Also look up the trans install on a '03 Expedition…

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Martin Technician
Waukegan, Illinois
Martin Default
 

Hi Tim, I service a Ford Fleet and I experienced this with a 2011 F350 gas engine probably in 2013 if I recall. The vehicle was repaired under warranty from Ford as it had just under 20K on it I believe. I was really surprised and I actually took the starter out myself just to see the flywheel and it looked just as bad as yours. This truck gets started daily multiple times and when I questioned…

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Richard Technician
Stony Brook, New York
Richard Default
 

Just to add to what you said, I looked at the wiring diagram and there is a starter relay in the circuit. I could see that sticking on and causing the vehicle to crank to long and breaking the teeth on the flywheel.

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