Here Are 7 Common Signs of Transmission Failure

What Car Owners Need to Know

• Since modern automatic transmissions are generally seamless, any noticeable issues — such as slipping, delayed engagement, harsh shifting or a burning smell — are important warnings that should prompt an immediate diagnosis.

Modern automatic transmissions are virtually seamless in operation. Aside from perhaps a little “jump” when shifting from Park into Drive or Reverse, they generally perform their duty of changing gears with little fanfare. Thus any time you notice something doesn’t feel or sound right … it’s probably not. Keep reading to find out what to look for when determining if your transmission is on its way out.

Common Symptoms of a Failing Transmission

1. The transmission slips, which means the engine revs up higher than normal without the car gaining much speed.
2. When shifting out of Park, there’s a long delay before Drive or Reverse is engaged.
3. You notice shaking, particularly when the transmission is changing gears.
4. The transmission shifts erratically between gears when you’re driving at a steady speed on a level road.
5. The transmission shifts very harshly or slowly.
6. The transmission sticks in one gear or seems to pop out of gear while driving.
7. You notice a burning smell, which could be due to any number of things, but one is the transmission overheating.

Related: Do You Really Need to Change the Transmission Fluid?

DIY Check of Transmission-Fluid Level and Condition

As far as the transmission itself goes, less serious problems that could cause the car not to move in gear include low transmission-fluid level, dirty transmission fluid or a clogged transmission-fluid filter.

The first can usually be determined by pulling the transmission dipstick and checking the fluid level. (Note that some newer automatics don’t have a transmission-fluid dipstick.) This will also allow you to check the condition of the fluid, which should usually be red; if it’s dark, smells burnt or has lots of metallic flecks in it, that indicates a problem. If that’s the case (and the fluid’s not low), “fixing” this will require at least removing the transmission pan — as will replacing a clogged filter. Transmission fluid should be changed periodically according to the manufacturer’s recommendations, which is typically between 30,000 and 100,000 miles.

To check your vehicle’s transmission fluid, follow the manufacturer’s instructions in your owner’s manual. Some automakers will recommend checking the fluid with the car running and others with it off. Note that there are several different types of transmission fluid, so make sure you get the right one for your car. Also note that if the transmission-fluid level is low, the fluid likely leaked out somewhere, so keep an eye out for indications of a leak.

Will the Check-Engine Light Say What’s Wrong?

In any of these cases — along with some more serious ones covered below — the problem may cause either the check-engine light on the instrument panel to illuminate (it may sound counterintuitive, but the check-engine light can also indicate transmission problems) or the illumination of a separate transmission warning light. If this is the case — and the fluid’s not low — getting the trouble codes read is your best next step. Any repair shop and most auto-parts stores should have what’s called an OBD II code reader (“OBD II” stands for onboard diagnostics, second generation) that can decipher these codes, and you can buy a basic one yourself for less than $30.

Which Parts Could Fail?

A problem that is more serious but often doesn’t require the removal of the transmission (a major job and thus expense) is a faulty shift solenoid. These are what activate the clutch packs or bands inside the transmission that engage the proper gears. Shift solenoids are likewise usually inside the transmission but are often accessible simply by removing the transmission pan.

Another possible cause might be a problem with the transmission control module — a computer that controls shifting — or with one of the sensors that feeds the TCM information. It could also be due to loose or broken wires leading to the TCM. While a TCM-related problem will usually prompt a warning light, a loose wire may not. As a new TCM can cost hundreds of dollars, it’s best to check the wiring before replacing it.

Almost anything else — which includes broken gears or worn clutch packs or bands deep inside the transmission — will probably require major repairs that can easily cost thousands of dollars.

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Signs It’s Not Transmission Failure

If you put your car into Drive or Reverse, hit the throttle, and the engine revs but the car doesn’t move at all, there are several possible causes — a couple of which don’t have to do with the transmission itself.

One that isn’t the fault of the transmission has to do with the linkage that connects the shift lever either to the transmission or to a computer that controls it. If the linkage breaks or gets out of proper adjustment, the shifter may be in Drive or Reverse, but nothing is telling the transmission to be. This will usually result in there being no subtle “jump” as there normally is when you put the shift lever in Drive or Reverse. One thing you can try is to depress the button on the console shift lever (or pull in the column lever) and slowly move the lever back and forth a bit to see if you can feel the jolt of the transmission shifting into gear.

Another — though less likely — “non-transmission” cause is that the driveshaft (on rear-drive cars) or constant-velocity axle (on front-drive cars) is broken. In that case, the transmission is going into gear, but the power isn’t being sent to the wheels. This is less likely to be a problem upon start-up because the driveshaft or CV axle more commonly breaks as you’re driving down the road — and that will make a noticeable noise before the car coasts to a stop — though it could possibly happen when the transmission is shifted into gear from Park.

With any of these issues, even though the car is still drivable, it’s best to get the problem checked and corrected as soon as possible, as it could easily get worse — not only leaving you stranded, but causing greater (and more expensive) damage.

 More Transmission Advice From Cars.com:

• Expert Advice on Car Maintenance
• Are Manual Transmissions Cheaper to Repair and Maintain Than Automatics?
• Why Does My Automatic Transmission Act Funny?
• What Does an Automatic Transmission Do?
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