What is an overdrive pulley?

Is it safe to drive a thunderbird in overdrive?

• My friend has a thunderbird and he thinks the overdrive is backwards. It's an automatic, and on the dash it has park, neutral, overdrive, then drive, then first gear. He thinks that Overdrive and drive is backwards so he keeps driving it in overdrive because he says the RPMs are running too high. I told him overdrive is meant for higher speeds. I just need some more opinions here, because I've heard that you can screw up your transmission if you run overdrive in a lower gear. Any suggestions here?

• Answer:

  In any modern car you should always drive it in overdrive unless you are going up steep hills. An automatic transmission selects the proper gear for the speed you are driving automatically. When he is stopped or going slow the transmission will downshift just as if it was in drive. when he accelerates it will use the appriate gear for the speed. Drive simply locks out the overdrive gear and keeps it in the 1:1 gear (3rd gear in a 4 speed), for more torque but less fuel economy. Driving it in drive at high speeds will damage the engine. The only time you should use Drive and (1) or LOW in some cars is when the amount of torque you need is not your speed and there is an extra load on the car. I.E. when you are going up a steep hill or pulling a trailer. Many cars will use the MAF to detect the grade and downshift accordingly whithout you doing it. Pitting it in drive just keeps it from switching back and forth when the grade fluctuates.