if you want to go fast, then you change gear at redline. if you are driving normally usually 2-3k
For second gear about 1500 rpm is easy on the engine. 2100 rpm is good for third gear when you are driving around the city. This varies depending on your car's specifications and how powerful it is.
rpm too low maybe you are shifting to soon
you are going too slow for that gear your engine has very little torque at low rpm
you may not be at a high enough rpm
rpm goes up and does not change gear below 60
Gears in a car change where the powerband (or Torque) are in the RPM range relative to what gear it's in. When a car is put into 1st gear, the "power" in the car is very very low in the RPM range and this is why a car is put into a low gear when climbing a hill or steep grade.
2003 Ford wind star LX mini van does change to second gear except when placed on 2 and it does not speed.
because you are engaging the clutch which cuts out the engine for a smooth gear change
If would not be bad for a car engine to shift from third to second gear if you are traveling at 30mph.
It changes the gear change rpm in you automatic transmission. It will rev out to higher rpm before changing into the next gear which will make your acceleration quicker and make the car more responsive but you will use a little more fuel. It doesn't actually give your engine any more horsepower as such.
Is that when you shift INTO gear? It's supposed to drop a little - 150 to 200 rpm - when you put the car in gear. If it drops 500-600 rpm, start by looking for vacuum leaks.
That would be the second gear of your automatic transmission.