Q: My 2004 suburban has D 3 2 1 what should I drive in D or 3

The computer controlled automatic transmissions in today’s vehicles are designed to be completely intuitive. You will not gain any performance advantage, or gain in fuel economy, by driving around town with the shifter in the 3 setting. For the best performance, simply put the shifter into the D (or drive) position and drive normally. The only caveat is when towing a load that is equal to, or more than, 75% of the vehicle’s towing weight capacity. When towing a heavier weight, it is recommended to engage the tow function on the transmission by depressing the button located on the end of the shifter. Depressing the tow button tells the transmission to expect a larger load and it will use a different set of parameters for shifting. So, unless you are towing fairly heavy loads, it is best to just put the shifter into the Drive position.