Defective Flexplate

[jayb]

What do you guys think of this?  This is a brand new Performance Automatics flexplate that I installed in my Galaxie.  After a few hundred miles it is missing 7 teeth.  Here's a photo of some of the teeth that were broken off:



Looking at the broken areas it appears to me that the metal was not heat treated or hardened properly, resulting in extremely brittle teeth that failed easily.  The flexplate was used with a factory FE block plate, so I know the starter was indexed properly.  The starter drive shows no signs of wear.  I checked the diameter of the flexplate and it is identical to the others I have here.  I did not engage the starter with the engine running or anything like that.  The seven teeth are missing in various spots around the outside of the ring gear, not in one area.  The three shown in the photo are the ones that are closest together.

Did I get a bum flywheel?

[Bullitt]

The teeth don't match the compression strokes of 4 cylinders?

Josh

[WConley]

Jay - That should never happen.  The ring gear either has the wrong composition or it was cooled too quickly during heat treatment.

Those are brittle fractures.  A normal ring gear has sufficient toughness in the material that you won't see that brittle behavior.  I'd look into a free replacement!

[machoneman]

2X to Bill's reply. I had seen/read of similar tooth decay (!) a few years ago on other forums but can't say it was the same supplier. Seems the heat treat was quite uneven on one side of the ring gear and lots of folks (not just Ford fans) had similar issues. But it was awhile ago.   

[jayb]

The teeth don't match the compression strokes of 4 cylinders?

Josh

Well, kind of.  They are broken roughly in 90 degree increments around the flywheel, except for one of the four spots where the teeth are intact.  But two teeth are broken together in only the one spot in the photo.

[jayb]

Jay - That should never happen.  The ring gear either has the wrong composition or it was cooled too quickly during heat treatment.

Those are brittle fractures.  A normal ring gear has sufficient toughness in the material that you won't see that brittle behavior.  I'd look into a free replacement!

That's kind of what I figured too, Bill.  I will be contacting Summit (where I got the flywheel), and maybe Performance Automatics.

[Barry_R]

I'll agree with Bill - too hard/brittle.  The four spots correspond to the compression pints in the engine - that's where it'll always stop - and fail because of the highest crank loads.

[manofmerc]

After the pioneer flexplate on my 427 comet broke I to bought a performance automatic flexplate from summit .It was sfi approved and had a nice paintjob on it .Upon taking it out of the package I found it to be identical to my busted pioneer .I micd the thickness and they were the same About .078 I believe .Same holes in the same location .Performance auto just takes a pioneer flexplate and paints them puts a sfi sticker on and charges you about $120 more than a pioneer flexplate .I sent that crapper back and got a real flexplate .I bought an ati nice and thick good clean welds with lightening holes around the perimeter of the flexplate .It isnt cheap though with the adapter you have to buy over $300 .I dont think I will have flexplate issues again though .They have them with or without the external weight for 428 cranks .I had to have one for the 428 crank because my combo is 427 block with 428 crank .My flexplate had cracked all the way around under the bolt ring .Sounder like a threshing machine .This same engine broke the input shaft on my c6 couple years ago .That sounded like a hand grenade .Doug

[Cyclone Joe]

Looks like the case hardening process that is done on the gear teeth went on for too long, resulting in a brittle root, or the tempering process was missed altogether.

Joe

[Qikbbstang]

if their lucky.  They makee lookee nicee....  What,,,,,Now you want heat treating also ?......

Please don't take it as picking on you, but I have to wonder if those teeth would have ever given up the ship on a 360 Cu In 9:1 2V truck motor.