From what I understand, the pulley is built so that it will not over-rev, it will dampen sudden rpm changes, and will not turn backwards. That's what my alternator rebuilder told me, and that it costs $80, so I was lucky that mine was still good or the build would've been more expensive.
Mine failed at 140k/7yrs. It failed due to everything inside of it that could go bad being bad: field brushes, bearings, VR.
I have seen where some people have had their alternator go out at an earlier time either in mileage or years. I think most of those were VR failures. Back in the day- before fancy pulleys, but after internal VRs- alternators would last about 60k miles. Really, the lifetime of a car back then was under 100k for most people. That's about the point where you were replacing everything, and what's the point in keeping a car that long? I think most people who cycle through vehicles only got 60k out of theirs, or did lease programs. Lifetime alternators were a godsend for used car buyers because the chances were pretty good that even if you took care of the vehicle you'd go through at least 2 alternators before you got rid of it.
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Originally Posted by the user formerly known as ZX3_Chick
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