How do you tell when car is in over drive?

Answer 1

If you have a digital display which tells you the gear the vehicle's in, the gear it's in can tell you if you're in an overdrive gear or not. However, you have to know your transmissions. For example, in a transmission such as the 4L60E or 46RH, only the fourth gear is the overdrive gear, so you know you're in overdrive when you're in that gear. The 6L80E has two overdrive gears, so you're in overdrive when you're in fifth or sixth gear.

The other way involved a bit of mathematics, and probably isn't that practical to try doing while the vehicle is in motion. You would also need to know your transmission final drive ratio and your rear end gear ratio.