About Kickdown Switch: If you’ve driven a vehicle with an automatic transmission, you must have experienced downshifting when you press the gas pedal hard on the floor.
This downshifting is a result of a kick-down switch.
You can manually downshift vehicles with manual-mode transmissions or paddle shifters, but conventional automatics employ kick-down switches.
Let’s look at the function of this switch and its operating mechanism.
Table of Contents
- What Is a Kickdown Switch?
- Kickdown Switch Operating Principle
- Do Vehicles With CVTs Have Kickdown Switches?
- Is Kickdown Harmful to Vehicles?
- Kickdown Function Safety Features
- Wrap Up
What Is a Kickdown Switch?
The purpose of automatic transmissions is to simplify the driving experience, and a critical component in the system is a kick-down switch.
This device sits on the vehicle’s floor behind the gas pedal assembly. When you push the pedal to the metal, the gas pedal will press this switch, activating it to downshift the gearbox.
Reasoning Behind Kickdown Switch Implementation
Besides simplifying driving, automatic gearboxes attempt to lower the engine RPM by engaging the highest gear to minimize fuel consumption.
However, these high gears give the vehicle low torque. And you need high torque when going uphill or overtaking.
So, when you push the accelerator pedal hard, it will contact the switch, which will downshift the gearbox to give you the required torque to drive the vehicle at higher speeds.
A brake and accelerator pedal in a car with an automatic transmission
However, the vehicle can only engage in kickdown mode if the engine runs at low RPM (when you are cruising at high gears).
Therefore, you can only engage the feature when driving at high speeds.
The transmission will transition back to normal mode after you let go of the gas pedal, resuming driving at the high gears to reduce engine fuel consumption.
Kickdown Switch Operating Principle
The kick-down switch does not connect to the automatic transmission directly.
Instead, it sends a signal to the vehicle’s ECU, informing it the vehicle requires urgent acceleration.
The ECU responds by downshifting, enabling the engine to hit a high RPM to hasten acceleration.
A vehicle’s ECU
When the vehicle transitions to kickdown mode, it applies an electric current to the kickdown solenoid, which opens the kickdown valve in the transmission’s valve body.
This valve then applies pressure to 1-2 and 3-4 gears to increase the RPM and torque.
After releasing the accelerator pedal, the ECU cuts power to the kickdown solenoid, but the valve remains open.
As you step on the pedal lightly to increase the RPM, the pressure gradually closes the valve.
The solenoid pack of a 7-speed automatic transmission
Do Vehicles With CVTs Have Kickdown Switches?
Continuously Variable Transmissions (CVTs) are relatively new compared to the traditional torque converter automatic transmissions.
Modern vehicles have responsive transmission systems that feature computer-assisted transmission control.
Therefore, these CVTs and the newer automatic gearboxes don’t rely on input from kick-down switches.
A continuously variable transmission (note the steel belt)
ECUs in these vehicles monitor the vehicle’s current speed with the gas pedal’s position using the accelerator pedal sensor.
If the car is not accelerating as much as it should, these ECUs trigger downshifts.
And the computer can activate this downshift by more than one gear.
So, you don’t have to push the pedal to the metal to activate a kick-down in modern vehicles.
More recent vehicles have different driving modes that tune the vehicle to suit driving conditions like sport, comfort, and sport+.
In such cases, the computer also tweaks the trigger point for activating a kickdown.
For instance, in sport or sport+, the ECU increases the RPM for upshifting to the higher gears, meaning the vehicle will kick down faster.
The result is sharp acceleration even when you press the gas pedal slightly but at the expense of fuel economy.
A drive mode knob selector with a sport mode option
Is Kickdown Harmful to Vehicles?
Kickdowns increase the engine’s RPM for faster acceleration. Therefore, the function overworks the engine and transmission, increasing wear.
However, the feature is not harmful to vehicles because car manufacturers cannot include something that damages their products.
Although manufacturers make automatic transmissions to handle smooth motion, they can withstand aggressive acceleration.
Most vehicles have monitoring systems that activate together with the kickdown mode.
The ECU takes in different variables, such as RPM, speed, throttle valve position, and current gear, then engages the most suitable gear permissible at the current velocity and RPM.
Therefore, it cannot downshift from the 6th gear to the 2nd or 1st gear. Maybe 5th or 4th.
A cross-section of an automatic gearbox
Situations Where the Kickdown Feature Can Damage Vehicles
Old Automatic Transmissions
Automatic transmissions in old vehicles operate differently from those in new cars because their kick-down switch kit uses a control cable for physical pulling to activate the feature.
Control cables might not be as reliable and accurate as computer-controlled kickdown mechanisms.
They can get cut or fall out of alignment, causing sharp, frequent accelerations that can stress the engine or transmission systems.
Cars with Transmission Issues
Also, straining vehicles with transmission issues can cause permanent gearbox damage.
This factor applies to transmissions in old and new vehicles, especially those running on CVTs.
The CVT steel belt can overheat the CVT fluid (due to slipping) or even snap, and it is expensive to replace.
Kickdown Function Safety Features
Modern vehicles feature a transmission control module that protects the engine and gearbox from overheating if you redline the car.
This TCM safety feature can prevent a kick-down if the lower gears can raise the RPM to the point of causing engine damage.
Therefore, even if you try to push the gas pedal to the metal, the gearbox will not downshift.
But the vehicle will accelerate, albeit in 5th or 6th gear, giving you low torque to overtake.
Wrap Up
Although kick-down switches are no longer present in the automatic transmission systems found in newer cars, the computer-activated kick-down mode functions the same way.
Only the implementation mechanism differs.
Therefore, you should take your vehicle to a mechanic to check your vehicle’s transmission or engine if you fail to get a punch of power when you push the accelerator pedal hard.
It might be the kick-down system or the computer preventing further damage to other critical components. Most people confuse the kick-down switch with transmission overdrive, so read this article to learn more about the latter to differentiate the two.
