When you find out that your car has transmission problems, it can be like someone just placed it on death row or sent it off to the gallows. Transmission problems are among the most significant issues with a vehicle and can cost enough to place a death sentence on a car, truck, or SUV. Or on your wallet. If you know the signs of a failing transmission, you might be able to head off major problems by addressing them early on. And if you know what to look for, you can avoid buying a car that already has transmission problems.
What is a transmission?
Your engine, whether it is a fuel-saving four cylinder or a seven-hundred-plus horsepower Hemi, can do nothing to move your motor vehicle. The engine provides power in the form of torque as its crankshaft rotates with the movement of the pistons. But power needs to make its way to the wheels. That responsibility falls first on your transmission. Its job is to “transmit” torque from the engine to the rest of the drivetrain, to the axles and the wheels, through a series of gears or belts, so that your car can travel over a range of speeds. The concept is similar to the gears on a bicycle that allow a rider to start off easily in a low gear and shift through higher gears as speed increases.
Transmissions come in manual and automatic models. A manual transmission, or “stick shift”, requires a driver to decouple the transmission from the engine (with the clutch pedal) and shift gears upward or downward manually. An automatic transmission, once placed “in gear”, does the whole job without any thought from the driver. While manual transmission drivers find a loyal following, only two percent of passenger vehicles sold in the U.S. include a manual transmission. Most drivers prefer the ease of an automatic.
Two types of automatic transmission
An automatic transmission allows your engine to rotate at an optimal rate, neither too slow or too fast, while providing just the right amount of power to the wheels necessary at a given speed. It does this by connecting complex sets of gears of different sizes to create the necessary ratio of torque. Hydraulic oil (transmission fluid) is used to control the gear sets, and a fluid-filled torque converter decouples the engine and transmission so the gears can be changed with little drop in engine rpms. The whole system is overseen by a computer module that senses engine speed and throttle position to shift the gears up and down as necessary.
In recent years, a different type of automatic transmission has become increasingly popular. Rather than rely on gears that need to be shifted, a Continuously Variable Transmission (CVT) functions in much the same way that a snowmobile does. It uses two pulleys, one on the engine side and another on the drive side, with a belt running between them. The pulleys are able to change sizes, effectively altering the ratio of power to the wheels. Since no gears are used, a CVT does not need to shift at all. It simply changes ratios “continuously” from slow to fast and back again. Some CVT transmissions have designated points programmed into the control module in order to simulate the feel of changing gears, but that has more to do with providing a familiar experience to drivers than it does the operation of the transmission.
In either case, a traditional automatic or a CVT, problems can occur and repairs can be costly.
What are some signs of a bad transmission?
Obviously, not all transmissions are alike. Neither are the symptoms when they go bad. But the symptoms are similar. Because the majority of cars on the road feature automatic transmissions, we will focus on those here. But a manual transmission can show a similar set of issues.
Pay attention to these signs of a transmission that is having problems, especially if you are evaluating a vehicle for purchase:
If your transmission feels like it is not shifting on time, as if the engine is revving too high and shifts are coming late, you could be having transmission problems. Likewise if your transmission seems to be going through mood swings, shifting at odd times or hesitating and jerking. Low or contaminated transmission fluid or worn transmission parts can cause erratic shifting.
Transmission is slipping
Most cars include a tachometer on the dashboard that traces the speed of the engine in rpms. If you see the needle of the tachometer rising but your speed is not increasing, your transmission might be slipping. Same goes if you hear the engine racing, but you feel like you are going nowhere fast. Transmission slipping can be caused by low or dirty fluid. But internal wear can also be the culprit. (With a manual transmission, this symptom could mean that your clutch is failing).
Your transmission will not engage or remain in gear
If you shift your vehicle into drive and it will not move at all, the fluid could be extremely low. The shifter cable or shift mechanism could also be the problem. But an issue in the valve body of an automatic transmission cannot be ruled out. Also, modern automatic transmissions rely on messages from the control module to know when to work. The module might need to be scanned to find the cause of trouble.
Vehicle has no power
If your car seems to have little or no power but your engine is running as it should, the problem could stem from dragging brake pads, a faulty brake caliper, or the engine control module limiting the power because it detects an issue. It can also be caused by an internal transmission problem.
Low or leaking fluid
A common cause of transmission failure is low trans fluid. Many transmissions today are not user-serviceable, meaning there is no way for the operator to check the fluid level. No dipstick. Look for signs of leakage underneath the vehicle. Transmission fluid is red to reddish-brown in color and can be coming from one of the hydraulic lines, from a seal at the radiator (or transmission cooler), or from the transmission itself. Low fluid level can lead not only to problematic symptoms, but to complete transmission failure.
A burning smell can come from any of several sources, especially if a leaking fluid (engine oil, power steering fluid, etc.) falls on a hot exhaust component. Transmission fluid is no different. But it can also cause a burning smell if the transmission is overheating. (A manual transmission clutch that is worn out can cause a burning smell, different than burning fluid)
If your automatic transmission is having problems it could cause your engine to overheat. If you see the engine temperature gauge spiking or see steam coming from under the hood, pull over and allow the engine to cool down. A number of problems can lead to engine overheating, including a bad serpentine belt, water pump, or engine coolant in poor condition.]
Strange noises coming from the transmission
A whirring, whining, humming, clicking, or buzzing sound coming from the transmission is not a good sign. Really any strange noise coming from your transmission is out of place. Certainly any grinding noises are a no no. A screech or whine that races when you press the accelerator pedal, especially when you have poor acceleration, can be related to a bad belt in a CVT transmission.
Check Engine light comes on
Often (though not always) a faulty transmission will trigger an engine diagnostic code and trip the Check Engine Light to let you know. Same goes if your engine overheats because of a bad transmission. Problems with a solenoid, speed sensor, slippage, and more can cause the Check Engine Light to come on.
Transmission problems can be serious – and cost you serious amounts of cash. If you notice any of the signs listed here, make sure to have your vehicle inspected as soon as possible to head off problems before they get worse. Because low transmission fluid is such a common cause of many transmission symptoms, it is important to keep it topped off and in good condition. But access to the transmission fluid on most vehicles today requires special tools available to trained technicians. Some repair shops offer a free courtesy check whenever you take your car in for routine or general maintenance. Otherwise, it is a good idea to have your vehicle thoroughly inspected on a regular basis to avoid problems, including and especially transmission problems. And if you notice any of these signs when you are test-driving a vehicle for purchase, return it and look in another direction. Or else you might find yourself with a car that does not have much life left.