Just picked up my grandmas Nikon 70-200mm 2.8 with the silent wave motor. The lens makes a squeaking sound when focusing. What could this be and where can I get it repaired if needed? The lens functions good just makes a sound like it needs barring needs to be greased.

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Nikon D300
Nikon D80/MB-D80
Nikon 80mm-200mm 2.8
Nikon 70-200mm 5.6
Nikon 18mm-55mm 5.6