They are out there, were pretty common on GMC chassis, I have seen them on late 80's stuff, maybe into the early 90's. I wouldn't call them great technology, they had a tendency to be quite troublesome, even when driven correctly. It was hard to find a driver that didn't beat them, and when you did, the motor would hang up, or something else would fail.
Why arre you asking?
"It's always wrong, everywhere, for anyone, to believe anything beyond insufficient evidence" -- William Kingdon Clifford
John (N9MXX) & Derek (KC9KEM)