You can also use a section of broom stick to listen for where sounds come from. The stick on the Alternator and the other end on your ear.

Watch out for moving parts.

I would worry that you are going to get made in China bearings (which cost about 2-3 dollars on ebay) from rock auto.

If you have the time you can take apart the alternator and the number of the bearing will be on them. Go on ebay and find a source that has USA or Japanese made bearings.

Note when I changed the Bearing on my alternator I found that the Alternator had a sticker saying rebuilt by Bosch North America. Chinese Bearings were inside.

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84 300D, 82 Volvo 244Gl Diesel