My Bissell vacuum cleaner makes a loud screeching noise, how do I make it stop?

It's a Bissell Multi-surface Easy Vac. Next month it'll be a year that I've had it. Whether I'm vacuuming the floors or using it in 'Dust Buster' mode, it makes a terrible screeching noise. And yes, I clean it out everytime. It's so bad that I have to wait for everyone to leave the house and I have to wear ear plugs while using it. Even when I'm downstairs at the furthest part of the house, people upstairs are disturbed by it. I don't want to bust anyone's ear drums!!! For 2 weeks it didn't make this noise and then started up again. How do I stop it or which new vacuum cleaner should I use? I really like this one because you can switch between carpet + carpetless floors with a flick of a switch, it's small so it's easier to carry up the stairs AND you can take it apart into Dust Buster mode, very convienent to hold when you're dusting the top part of a hutch (or any furniture that's close to the ceiling). So, please advise to something similar. Thanks!