Kind of a grey area on the Volt.
Shocker: Volt's gas engine is indeed mechanically connected to the drivetrain (updated with GM engineer's response)
Interesting news from General Motors today that's resulted in some puzzled expressions at Engadget HQ. We've learned that the Volt, which Chevrolet has been making quite a fuss about calling an "extended range electric vehicle," is actually just a traditional hybrid with some... potentially...
www.engadget.com
Basically, the Volt's ICE is coupled to the ring gear within the transmission, which at times spins up to provide direct mechanical power when the batteries are near depleted.