Oil prime

2004LB7

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Those look like fatigue cracks due to constant flexing. Id make sure the transmission was seated to the engine correctly and flush. Also no debris or anything stuck between the converter and flex plate or transmission and engine. Just a small amount of continuous flex due to a misalignment can do that
 
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ikeG

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Those look like fatigue cracks due to constant flexing. Id make sure the transmission was seated to the engine correctly and flush. Also no debris or anything stuck between the converter and flex plate or transmission and engine. Just a small amount of continuous flex due to a misalignment can do that
I didn't see any issues taking it apart. Not sure what to think

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TheBac

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I can remember seeing that on higher-hp trucks in the past, but not stock. Did anything else seem odd when you took it apart again?

EDIT: you answered that earlier.

Must've just been fatigue from use.
 

ikeG

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Washer
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Chevy1925

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Any idea where the heat marks on the flex plate came from? Theres two spots that look like they got hit with a torch. Could have harden there, cracks started and bye bye
 

ikeG

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It does look like that but that could be from the friction while running it. He actually drove like this for a while, towing snowmobiles. An employee did this job from start to finish in Aug, he's quit Dec 31. But even if he took a torch to the flywheel bolt heads I don't think it gets spots like that.
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JoshH

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I think James is on the right track. I bet your former mechanic heated the bolts with a torch and got a little wild with the flame.
 

Chevy1925

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Definitely a “who came first, chicken or egg” situation. I can see how it could be either way. Since it junk, could try hitting it with the mapp gas and see how long it takes to turn it color
 

2004LB7

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While they do look like heat marks, the HAZ looks too small or narrow to me for a MAP gas torch. Maybe a quick mig or tig on the backside. But that would be obvious.

Maybe take a sharpened punch and with some light hammer taps, see if any of those spots seem harder or softer then the rest. Not too accurate but maybe enough to tell the difference

I'm going to stick with the transmission not being perfectly flush with the engine.
 

2004LB7

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And this is after map gas torching directly on flexplate for 20 seconds
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That is more what I expected the HAZ to look like. The previous one is too small makes me suspicious if it even is heat related

Can you tell if there is a hardness difference between the torched areas and unaffected?