3 years ago, and about 4500 miles, i did a trans rebuild and picked up one of them 10" b&m holeshot converters ( couldnt afford a good one at the time)
the converter was never really efficient, i think it was maybe 7 or 8% slip when new.
about a month ago i started the car and heard a quick clingy clang sound for maybe a second, then went away. i thought it was loose converter bolts, checked em, and they were good, checked over everything else and things are solid.
i passed of that initial racket as somethin minor as it dont happen all the time, just every 3rd or 4th time i start the car, and only for a second.
decided i would run the car last weekend at the track, mph didnt seem to make sense with my rpms at the stripe...went home, ran the numbers, and come up with 14-15% slip!
im now thinkin i got a broke fin in the converter, or really bent at best.
What the heck causes this??? Im not making ridiculous horsepower, well within the limits of what B&m says the converter will handle? Less than 5000miles on it....street/strip.
Ive learned my lesson on cheap parts, but good lord,shouldnt a 400$ converter should last a little longer behind a 400hp 340??

Heat is there enemey.

As the converter changes in either RPM or in Torque load,
the metal in either impeller or pump 'flexes' a little,
and this eventually causes metal fatigue.

It is also possible that the metal had a flaw from the beginning, which greatly shortens the time before a fatigue failure.

Quote:

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What makes a converter go bad

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Hanging out with trannies...

Sorry, I couldn't resist!

As the converter changes in either RPM or in Torque load,
the metal in either impeller or pump 'flexes' a little,
and this eventually causes metal fatigue.

Does that make it a bad idea to use a stock converter with 100k miles on it?

and can you eff the trans up much by driving with a broken fin in the converter?
now im scared to start my car!

My B&M converter did the exact same thing. It made the "loose flexplate bolts" sound, but only intermittently. I began to worry when I would get a hairy pan magnet every 400 miles. I knew something was wrong, but the trans always performed flawlessly and being in a '73 B-body I didn't want to drop the trans. That was a mistake: by the time I dropped it, the grenading converter had wiped out the stator support and input shaft.... The B&M converter couldn't hang behind a stock smog 440 for 5000 miles. It's the last B&M product I'll ever own.