Sounds like a bad bearing in the power nozzle. Those power nozzle motors are very simple to disassemble and clean. I have never serviced the sealed bearing on one though. Luckily those motors are fairly easy to get a hold of. They can be costly though.
As ridiculous as this sounds, you may even find an entire power nozzle cheaper than the motor itself on eBay!! From there you can switch your top hood or switch the motor or just use the freshly purchased power nozzle as is. It may even be an upgrade to yours with a headlight and dual row brush roll!!
The motor for your machine has a triangular formation screw connection to the base. Any motor from any PowerMax, Futura or Windtunnel---original generation style, power nozzle will work. Also Turbo Power 5000, 6000, 7000, 7500, Encore Supreme, any of those power nozzle motors will work.
Depending on the one you get, you could convert any T shaped 3 prong wire to a standard 2 prong wired for the power nozzle! The only reason for the 3 pin system was for the headlight to run on a separate terminal that would stay running while a brush roll on/off switch cut off power to the other 2 terminals which powered the motor.
As you can from the inside of my Windtunnel power nozzle below, it is the same motor design as what would be in your Futura!
What would not fit in your nozzle would be a motor for a Quadraflex PowerMatic or Celebrity Powermatic!! Nor a motor from current market compact style Hoover power nozzles.
