While your vehicle’s engine may create the inertia to move forward, the transmission determines the speed based on the driver’s desire and sends the power to the wheels to maintain or increase the speed. When things are working well, you should rarely notice the transition between gears in an automatic, especially if the transmission happens to be a CVT.
When the transmission jerks between gears or the transmission is shifting hard, it should be taken as a warning that your transmission needs repair. When a transmission is shifting hard or slipping it’s time for an inspection. An inspection by an expert will tell you whether a simple fix can address the issue or major repairs are due.
Many symptoms exist that indicate the transmission is not operating as well as it should. The most common symptoms of transmission problems include:
1. Slipping Transmission
Slipping occurs when the transmission slips from one gear to the next, instead of gliding smoothly as it should. Transmission slipping can occur in one or several ways including:
- Interruption in acceleration
- Delay or failure to go into reverse
- Extremely high RPMs
- Check engine light on
- Burnt smells
- Difficulty shifting gears
- Shifting accompanied by strange sounds
Causes of transmission slips include:
- Low or Burnt Transmission Fluid – Low fluid can result in overheating and a deficiency in the creation of hydraulic pressure that is needed to engage gears. Fluid levels should be checked often either by you or a technician. Because the transmission is a sealed system, fluid loss is usually related to a leak. Burnt fluid can be compared to the smell of burnt toast and appears burnt as well. Burnt fluid is caused by an overheated transmission or a lack of maintenance which is a bad sign. Once the fluid is burnt, it may already be too late–the transmission may already be damaged.
- Faulty Clutch – Both manual and automatic transmissions use a series of clutches that aid in changing gears. Automatic transmissions are equipped with clutches in the torque converter that lock up at high speeds to prevent slipping, as well as in other areas throughout the transmission that can wear or burn out due to a lack of transmission fluid.
- Worn Out Gears or Transmission Bands – With use and time, it’s possible for gears to wear out. When gears don’t properly fit together, they can create a jerky shifting experience. Similarly, transmission bands that are linked to the gears, in automatic transmissions, can wear down or break over time and require replacement.
- Difficulty with the Torque Converter – A torque converter receives the power from the engine and converts it into torque that the transmission uses to send to the wheels. Over time the converters can wear down, preventing the flow of fluid, which results in slipping among other problems.
- Failed Solenoid – The solenoid is an electro-hydraulic valve that controls the flow of fluid throughout the transmission. Damage or failure to this component can cause the release of too much or too little fluid into the system.
2. Rough Shifting or Jerking Transmission
A car that is experiencing rough shifting may have trouble accelerating, struggle to change gears, or lack a smooth transition. Rough shifting is often described as a clunk or a thud feeling when the vehicle shifts from one gear to the next.
Causes of rough shifting include:
- Transmission Fluid Low or Poor Condition – Vehicles low on transmission fluid or that are operating with worn out or contaminated fluid are likely to experience hard shift conditions. Lack of adequate lubrication within the transmission can cause several problems, including hard shifting. The fluid in your transmission should appear clean, light red in color, and somewhat transparent.
- Vacuum Troubles – On older vehicles, the transmission would know when to shift based on the assistance of a vacuum modulator valve. The valve determines the load of the engine via a hose, called the vacuum line, that connects to the intake, measuring the amount of vacuum within the engine. A bent, blocked, or detached vacuum line can alter the pressure in the transmission producing a rough shift.
- Faulty Sensor – Many vehicles today are equipped with loads of sensors that communicate to their internal computers, including some that influence the transmission to shift. If the sensors are not functioning properly or receiving the incorrect data, it can cause rough shifting. In some cases hard shifting could be caused by a sensor transmitting the wrong data from the engine. A failed speed sensor may signal that the vehicle is traveling at a higher or lower speed than it truly is.
3. Delayed Engagement (Delayed Gear Shift)
Delayed engagement is defined as the pause or delay in response that it takes from shifting from Park into a moving gear such as Reverse or Drive. The duration of the delay can be as quick as a few seconds and up to one minute. Delayed engagement should not be ignored and is a warning sign that your transmission needs attention sooner rather than later.
Causes of delayed engagement include:
- Low transmission fluid
- Poor fluid maintenance
- Failed transmission solenoids
Slipping, rough shifting, and delayed engagement troubles are often due to poor condition or lack of transmission fluid; that’s why it is so important to have the condition of your fluid checked and flushed every 30,000 – 50,000 miles.
If you experience any of the above symptoms while driving your vehicle and it’s accompanied by the Check Engine Light, have the vehicle inspected immediately. Ignoring the light could result in costly repairs that could have otherwise been avoided.