Dave,

You can replace just the fan portion of the alternator. Take the alternator
out and keep the shaft from turning by jaminng a screwdriver in the
remainder of the fan while having a bolt and nut on one of the eyelets of
the alternator. Use an impact wrench to loosen the big nut. Do remember to
check for any crazy shaft play (wonder if that will make past the censors?)
before loosening the big nut.  Not sure what would have caused your
failure. This is just a guess but maybe the vibration is actually the
uneven rotational mass of the alternator.

I hope that helps,
T.

On Tuesday, October 30, 2018, David Boan <dboan@outlook.com> wrote:

> I have a question about alternator repair.  A noise, like a vibration,
> started suddenly while driving.  On inspection I found that about 1/3 of
> the alternator fan had broken off and embedded itself in the engine cover
> (also making about a 1/2" hole in the cover).  My question is what might be
> the underlying cause, perhaps the end bearing?  Or just a metal failure?
> The alternator, which is Bosch and about 8 years old, seems to be charging
> fine but the vibration noise is still there.  Just replace the whole thing?
>
>
> Dave B.
>
> Boise, ID
>