benm,

When you take it out, you can examine it closer to determine failure. Rust accumulating about where the boot is held is not uncommon in the rustbelt.

That shaft is heattreated steel- I'm guessing if you look at it with a Loupe and good lighting, you should see fine striations close to the origination (probably rust or a gouge), then over cyclic forces it broke. As the crack grew, it grew faster, hence the cleanist looking steel would be the last bit.


Michael

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Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E