Overdrive versus D2

I have a 1995 toyota camry with a 4 speed automatic. I was wondering what the difference between D2 and overdrive is. From what I believe, D2 limits the car to the two lower gears while overdrive being off stops the highest gear (the 4th gear) from engaging thus limiting the car to only 3 gears. Why no just put a ‘D3’ mode instead of an ‘overdrive off’ mode. How is the overdrive mechanically different from the D1/D2. Can you shift from D into D1 or D2 without stopping the car? Because I know you can turn off overdrive without having to stop the car. Thanks.

You don’t have to stop the car to shift into D2 either. But yes, D2 I believe limites the car to the first two gears. On some models it starts the car in 2nd gear and locks out 1st gear, I’m not sure which it does for your particular car.

If you put shifter in D1 and take off it will stay in 1st gear,it would only go 25-30mph and motor would be “racing” or reving very high.
If you put it in D2 and start out it will start out in 1st then go to 2nd and stay there, will not shift into 3rd or D3.
I think you have a button on shifter that turns OD on and off. When off it will not shift into OD,4th gear.
It is best to leave OD on all the time. It will shift up and down at the correct time for best power and gas mileage.
You also have a button on the dash I think. It is a power-economy.When pushed in pwr should light up on the dash.
When it is like this it will down shift from any gear sooner to give you more power and it will keep it in say 2nd gear longer before shifting into 3rd gear.
While in this mode it feels like you have more power you will get worse gas mileage.
My advice after having a few of these is to have OD-4th gear on and PWR button off,No PWR light on dash but OD light should be lit on dash.