An automatic transmission knows to shift when you're trying to pass another vehicle, going uphill or downhill, or trying to accelerate. However, even though your transmission is automatic, you still have some control over when it shifts. By varying your driving habits and shifting to low gears during appropriate times, you can increase the power and efficiency of your car.
Shifting an Automatic Transmission
The automatic transmission in your car is computer-controlled to keep the engine running at an optimum RPM (revolutions per minute). Whenever the RPMs increase above the top limit, the transmission automatically shifts into a higher gear so that the engine will turn slower under the same power.
Likewise, when the RPM level decreases beyond the low limit (the engine is turning too slow), the transmission automatically shifts into a lower gear so that the engine will turn faster under the same power. Varying the way you drive can help you control when and how the car shifts gears.
Forcing your automatic transmission to shift into a higher gear is easy. Simply follow these steps:
- Press the gas pedal as hard as you need to in order to get the engine RPM level to increase beyond the transmission's "shift limit." You'll notice this happen when you press the pedal to the floor in order to pass someone or to accelerate quickly onto the highway.
- Once the transmission shifts, you can ease off the gas pedal slightly to keep from going faster than you'd like.
- After your car has gone up the hill, allow the transmission to downshift. This will happen automatically when the engine isn't required to work as hard.
The more often you allow your automatic transmission to naturally select the higher gears, the less fuel that your engine will consume.
You can also force your automatic transmission to downshift into a lower gear. Here's how to do it:
- As you approach a situation where you'd like to downshift, ease off the gas pedal.
- Allow the transmission to shift to a lower gear.
- Keep your speed constant to maintain this gear as long as you would like.
How to Shift In/Out of Low Gears
In instances when you want to shift in or out of low gears, the process would be similar to the general approach taken with manual transmission shifting except without the use of a clutch. Never shift into a low gear while driving at a high speed.
To shift into a low gear, do one of the following methods:
- If you are in "D," let your foot off the gas or brake until you slow to around 20-25 mph, then resume a steady speed.
- Switch to "2."
- If RPMs spike too high (to 4,000 or 5,000 RPMs), slow down a little.
- Follow the same process to go to "1." Slow down until you're in the 10-20 mph range before switching.
A simpler way to shift into low gear is as follows:
Wait until you've come to a stop at a traffic light or stop sign. While at a stop, shift from "D" to "1."
To shift out of low gear, do the following:
- While in "1" accelerate until the RPMs reach around 3,000.
- Switch to "2" while maintaining a steady speed.
- While in "2," as the RPMs reach 3,000, switch to "D."
When to Use Low Gears
There are circumstances when you'll need to use the lower gears labeled "1," "2," or "L." In every case, improperly using it can damage your transmission, so be careful.
Towing Heavy Loads
If you are pulling a large boat or you have a truck and the flatbed is loaded down with heavy equipment or supplies, you could damage your transmission if you don't drive in "low gear." This is because your transmission is programmed to operate and shift under the manufactured weight of the vehicle. When you significantly change the weight, it can have adverse effects on the transmission. Using a low gear to tow heavy loads ensures that the entire transmission keeps the engine running at higher RPMs in order to handle that heavier load.
Climbing a Steep Incline
If you are in a situation where you're driving up a very steep hill, like taking a tourist drive up on mountain toll road, the automatic transmission can be affected in the same way as if you were towing a heavy load. This is because gravity is pulling back on the vehicle and making the load on the engine much heavier. Use low gear whenever you're driving up a long, steep incline.
Riding Down a Steep Hill
Another technique that not everyone is aware of is using a low gear when driving down a long, steep hill in order to save your brakes. "Riding the brakes" down such a hill can overheat them, and in some cases, it can lead to failure. By switching to low gear and allowing the engine to "brake" for you, you are taking advantage of the compression of the engine pistons to absorb some of that force and slow your vehicle. You'll still need to use the brakes, but you will save them from some of the wear they would ordinarily experience.
Shift When You Want To
Normally, the point of an automatic transmission is to handle the shifting for you (unlike a manual transmission). But in some cases you, may need to shift the automatic transmission to a lower gear. By understanding when it's appropriate to shift gears and how to get your car to shift when you want it to, you'll be a much smarter driver.