Sound suggests badly broken drivetrain, but it's not that bad at all.
The Chevrolet Volt is often considered as a very reliable car, especially taking into consideration how complex the plug-in hybrid drivetrain is. However, one of the common issues with the 2011-2015 model year versions is the failure of the stator/rotor bearing - this is what happened to WatchJRGo's Volt at around 80,000 miles.
The car with the damaged bearing is still able to drive, but as you can hear on the video, the noise inside and outside is awful.
"The most reliable car in my fleet is down for the count. My Chevy Volt started sounding like Optimus Prime or a circular saw when it's in regen. This seems to be a relatively common failure as the mileage creeps up on early Volts. It's caused by the bearing cage failing on the stator/rotor bearing, rumor is the original bearing cage was nylon and the replacement is made of brass."
From the video description:
"TSB: PIP5081H: (EREV) Whine, Scrape, Whistle Type Noise While Driving - (Jan 8, 2016)
Models: 2011-2015 Chevrolet Volt 2014-2015 Cadillac ELR 2012-2014 Opel Ampera
Condition/Concern Some customers may comment on a whistle, scrape or whine type noise while driving that may be more noticeable during regenerative braking. Technicians may find this noise emanating from the left side of the drive unit (transmission). The tech may also state that the vehicle has a current or history code P0A46.
Recommendation/Instructions This noise may be caused by a separated electric drive motor B rotor bearing cage. A revised bearing has been released for installation into the drive unit. It is not necessary to remove the drive unit or motor for this repair. Follow SI (Document ID 2838728) on vehicle service, drive motor rotor bearing replacement procedure. During repairs inspect the end cover for any abnormal bushing wear, if found the side cover will also require replacement, however if no abnormal wear is found the cover can be reinstalled.
Important: Please ensure that the Special Tools DT-47865 - Bearing Remover and J-45124 - Removal Bridge are used to remove bearing. If proper tools are not used the rotor may be damaged leading to a repeat repair. DO NOT TRY TO PRY OUT. Important: To install bearing use Special Tools DT-22928-B Seal Installer per SI, as damage may occur if the proper tools are not utilized. Proper bearing orientation is the writing up or visible to technician. Please also order and replace the rotor shaft seal this could be damage during bearing removal or installation The side cover must be inspected in the bearing seating area as well as the bushing and resolver area. THE SIDE COVER AND THE TRANSMISSION COOLER MUST BE FLUSHED TO PREVENT RECONTAMINATION OF THE NEW BEARING. If the side cover or bushing are found to be damaged replace side cover. If any debris is on the rotor or side of transmission this should be cleaned/flushed with transmission still in vehicle. The transmission cooler also must be flushed. To do this the cooler thermostatic bypass must be removed."