Flex plate, teeth

[DaKing]

Back in Dec 2015 I had my transmission rebuilt. The shop did not notice cracked flex plate. (The transmission was already rebuilt, but only lasted ~5mi. The last trans builder messed up. he out of business)

In Jan, I pulled the Transmission and replaced cracked flex plate with a new ATP Flex plate.

After ~30 starts or about 2 weeks of driving, the teeth on the new flex plate are chewed down. Causing a no start issue, as there are no teeth to for the starter to grab.

Obviously I'm Livid, as I'll have to pull this transmission again. Jeep has long arms, so its a pain to pull.

Starter was original, teeth on the starter are a bit worn, but not bad. The starter was bolted tight to block. The engine to Trans is tight.

I'm looking of reasons as to why this would happen, so I can prevent it in the future.

first cracked plate :


Second broken teeth plate :

[SilverXJ]

Since your original flex plate showed little wear on the teeth and the new one died in short order I would just say it is a crappy flex plate.

[amceaglesx4]

Unless my pain meds are kicking in that's a flywheel. Flex plate is the thin aluminum shield. Hmm... only thing I could think of is the motor didn't want to turn over because it was frozen like a rock. The starter wanted to turn the engine and stripped teeth. Can't be a flat spot in the starter... how hardcore is your battery ? If its like mega cranking amps to the starter the starter would explode power and strip teeth. What I don't get is why the teeth are more chewed up closer to the trans. Its possible if the starter gear goes farther than it should it wouldn't make even contact with the starter. Few things to think about. More info needed I guess. Hope my rattling on gave you ideas.

[SilverXJ]

Unless my pain meds are kicking in that's a flywheel. Flex plate is the thin aluminum shield.

No, that is a flex plate. Manual = fly wheel, auto = flex plate.

[amceaglesx4]

Guess I'm used to manuals lol. I call it a flywheel

[jeepxj3]

Almost like the ring gear on the ATP flex plate was welded 1/8" further away from the crank/starter. Or a washer was used and spaced the flex plate further away from the crank/starter.
Or your starter is taking a dump and the gear is not fully going out all the way and engaging the ring gear.

Sometimes used 'original' parts are better than aftermarket, like engine sensors and here maybe flex plates.

[amceaglesx4]

Gotta disagree on most of that friend. If the started was going out it would have a flat spot , according to the one pic it looks like its engaging too far versus far enough. Weird ! What's the deal ? Old/ new started cheap/ huge amp battery, cold or fukin cold ? Let's figure this out friend.

[amceaglesx4]

Yea washers behind the flywheel lol would be a possibility too. That could probably be ruled out though.

[amceaglesx4]

I might have a flex plate for you I gotta look. If I do pay the shipping and its yours.

[SilverXJ]

Gotta disagree on most of that friend. If the started was going out it would have a flat spot , according to the one pic it looks like its engaging too far versus far enough.

how is that to be considered too far? The pic is from the front.

Weird ! What's the deal ? Old/ new started cheap/ huge amp battery, cold or fukin cold ?

It is neither of those.

After ~30 starts or about 2 weeks of driving, the teeth on the new flex plate are chewed down.

None of those causes would do that kind of damage in that short of a span. Also, consider his original flex plate looks fine on the ring. And he made no mention of the starter sounding like it is struggling.

Let's figure this out friend.

Poorly manufactured flex plate.

[amceaglesx4]

Alright good luck to ya friend. There's a reason why the teeth are so chewed up.

[DaKing]

Thanks everyone for your input.

Pulled the Transmission.

1st, no end play on crank
2nd, starter was tight, and trans to engine was tight.

Only a few teeth on the plate wore gone.

At this point, I think it was a combination of unique variables:

used starter with "ok" teeth.
bad fuel pump / prime issue, causing long starts with many cranks.
starter hitting flywheel as engine was already spinning.


I recall one of my starts grinding, cause I was still cranking after the engine had already started. My guess is that one start damaged the plate.

I need to fix my long start issue. Used to start with-in 2sec of turning key, now takes ~15 to 20sec....

[SilverXJ]

bad fuel pump / prime issue, causing long starts with many cranks.
starter hitting flywheel as engine was already spinning.

I don't think the long cranking is an issue. However, perhaps it coul dbe an issue on less than a perfect flex plate. If the long crank had anything to do with it it would effect all the teeth.

I recall one of my starts grinding, cause I was still cranking after the engine had already started. My guess is that one start damaged the plate.

That is a possibility, but since the starter was already engaged it shouldn't have caused an issue. Its usually when you try to start when the engine is already running is the problem.

I need to fix my long start issue. Used to start with-in 2sec of turning key, now takes ~15 to 20sec....

Check your fuel pressure prior to start and while starting. Could be a bad anti-drain back valve.

[DaKing]

bad fuel pump / prime issue, causing long starts with many cranks.
starter hitting flywheel as engine was already spinning.

I don't think the long cranking is an issue. However, perhaps it could be an issue on less than a perfect flex plate. If the long crank had anything to do with it it would effect all the teeth.

I recall one of my starts grinding, cause I was still cranking after the engine had already started. My guess is that one start damaged the plate.

That is a possibility, but since the starter was already engaged it shouldn't have caused an issue. Its usually when you try to start when the engine is already running is the problem.

I need to fix my long start issue. Used to start with-in 2sec of turning key, now takes ~15 to 20sec....

Check your fuel pressure prior to start and while starting. Could be a bad anti-drain back valve.

Thanks for your reply.

By "long starting" I mean it never starts on the first key turn. Takes a few key turns before it fires up. Because of the many key turns, one of the key turns happened once the engine was fired up. I now think this is what caused the teeth damage. I recall that start, hell, only had ~30 starts...

I was going to make a new post:
The start issue is fuel related. I have fuel pressure gauge hard mounted on the rail. At fist key turn pressure is not enough, takes a turn or 3 before required pressure is reached. Also, the pressure goes to zero with in 2 seconds of engine off. So the anti bleed back is faulty. Also fuel pressure never goes above 39# @ zero Vacuum. I have a 49PSI regulator installed. I also installed a new fuel pump. The whole fuel system is new or rebuilt. I have an external pump I'm going to mount for testing shortly.

The engine used to start on the very first key turn, in a second or 2. Lasted about a week, then needed many key turns.

[Cheromaniac]

Unless your fuel filter is heavily clogged, it does sound like the new fuel pump you installed was a dud.