I have my '76 on jack stands without tires since I was overhauling all of the brakes. In order to check the brakes with the booster on, I had the car running. Then I noticed as the car was running and in neutral, the back wheels (actually the hubs/rotors) were spinning very slowly. When I hit the brakes, they stopped spinning (proving my brake job went well

So I imagine while it's on the road, I won't even notice this symptom. But it struck me as odd and I just wanted to know if it was symptomatic of a bigger clutch, transmission, or throw-out bearing issue. Maybe the clutch should be adjusted?