HI, it's Jim from Crucial Vacuum!
If your Shark Navigator vacuum is only making a strange noise when the brush roll is turning then the two things to consider and examine would be the brush roll itself as well as the belt.
First off lets look at the brush roll itself. Right off the bat is there any noticeable debris caught in it? You're mainly looking for long carpet fibers, or even strands of hair? If so try using a scissor to cut the blockage away. Then, manually rotate the brush roll to uncover further clogs. When examining your brush roll take note of the condition of the bristles. Are they loose? If so this would be a good time to change your brush roll entirely. There should be two screws holding the plate onto your Shark Navigator. Use a screw driver to remove these screws to gain access to the brush roll and belt.
The second part to check would be your Shark Navigator's belt. With use the belt will stretch out, lessening the tension on the brush roll. Lesser tension diminishes the brush roller's turn rate and speed. So if your belt feels loose as well replace that. A general rule would be that you're going to want to replace your belt about every 6 months. And if your belt is really loose this could be causing a noise when your brush roll is active.
You can purchase your replacement parts for your Shark Navigator direct from Crucial Vacuum with free shipping and an exclusive 10% coupon for Fixya.com readers, use code: FIXYA10
I hope this was helpful. If you would like further assistance, please feel free to give us a call at 877.750.9239. We have helpful and friendly customer care representatives on the line ready to assist you.
Crucial Vacuum Customer Care