Posted on by Defensive Driving | in Defensive Driving Tips

Before reading this entry, you may want to check out my previous entry on how an automatic transmission works since this will provide some useful background information that will help you to understand how and why these transmissions can fail.

Unlike an engine, which can exhibit any number of odd symptoms when a problem occurs, an ailing automatic transmission will generally display one of a handful of symptoms:

  • Car won’t go into gear at all
  • Shifts are delayed or uneven (jerky or too sudden)
  • Unusual noises occur during shifts
  • “Slipping” occurs when the car is in gear
  • Car won’t go into low or reverse gears
  • Vehicle tries to move while in park or neutral
  • Shift lever is difficult to move

If the transmission won’t go at all (or if shifts aren’t smooth), your best bet is to check the transmission fluid. For step-by-step instructions on how to do this, see my previous entry on engine maintenance. You may need to add extra fluid if the level is too low. If this problem occurs repeatedly, it’s likely that there’s a leak in the system that will need to be repaired by a professional. Note that automatic transmission fluid is usually a deep red color, unlike engine oil, which is a light brown. If you notice red fluid leaking from your car or on your engine, then a leak is most likely present in your transmission.

A clogged filter could also keep a transmission from functioning properly. If you’ve never had your transmission’s filter replaced, have your mechanic do so the next time your car is serviced. The problem could also lie in the pump. If the pump isn’t maintaining fluid pressure, then the complex hydraulic system that powers the transmission won’t function.

Delayed engagement, i.e. a lag time between when you shift gears and when the car actually starts moving, can also indicate a problem with the transmission. This will be most noticeable when the car has just begun to run, so if you want to check for transmission problems, the best time to do so would be right after you’ve started the engine and are ready to drive. The transmission should engage almost immediately after a gear is selected. If this doesn’t happen, there’s likely a problem developing.

Delayed shifting is often caused by valves sticking the valve body, which prevents shifts from happening when they should. On newer cars, which control shifts using a computer, the problem could lie in the shift solenoids that are used to trigger shifts. If this is the case, these components of the transmission will likely need to be serviced or replaced. If the problem lies in the computer itself, then a reconfiguring of the computer is likely all that is necessary. Automatic transmissions also contain spring-loaded dampeners, called accumulators, which ensure that shifts happen gently. If the car suddenly jerks or slams into gear, i.e. the reverse of delayed shifting occurs, then the accumulators are likely to blame.
Slipping is another problem that can indicate something is wrong with your transmission. If you press the accelerator and the RPM increases but the speed doesn’t, this means that the transmission is going into gear but isn’t staying there. This is likely a sign that one of clutch packs or bands has burned out. Check your transmission fluid: if it’s dark, discolored, or burnt-smelling, then a ruined clutch is likely the culprit.

If the vehicle has difficulty with reverse or low gear, then the most likely problem is in the torque converter. The torque converter contains a one-way clutch that only allows components to spin in one direction. If this isn’t working properly, then the vehicle won’t go into low or reverse gears.
Finally, the problem could be purely mechanical, i.e. a broken component or stripped gear. Look carefully under the hood, as metal shavings or chips could indicate that one or more gears have been stripped. If this happens, you will likely have to have your transmission rebuilt.

So, what can you do to prevent these problems from occurring? The most important thing is to be sensitive to the sounds and functions of your transmission so that you can notice any odd behavior as soon as it begins. The transmission is a sensitive and complex system, in which small problems can very quickly escalate into major ones. Since this system is so expensive to repair, nipping any problem in the bud will save time, money, and hassle.
Even if you don’t notice any problems with your transmission, you should still check your transmission fluid twice a year. Maintaining proper fluid levels can help to prevent problems from developing. In addition to checking the level of the fluid, check the color and odor, just as you would when checking the oil level.

Next, remember that transmission oil, like engine oil, needs to be replaced at appropriate intervals. While a complete servicing done at a dealership will most likely include a change of transmission oil, your local mechanic may not do so at every servicing. Make sure that you keep complete and accurate records of your car’s service history, including each oil change. That way, you will know if a transmission oil change is overdue. For guidelines on when such a change must be done, see your owner’s manual, which will recommend the appropriate timeline for transmission oil changes and the grade of oil which should be used. Make sure that the oil filter is changed along with the oil. Also have your mechanic check carefully for any leaks in the system when the car is serviced.

Additionally, try to avoid driving behaviors that can place excess strain on the transmission. “Rocking” a vehicle to get it out of a snow bank or rut can easily destroy a transmission in minutes. This is because this “back and forth” gear shifting causes the transmission to heat up, which will result in rubber parts “like the very important seals and gaskets” failing. The transmission fluid will also burn off, and metal parts can warp. All of this leads to a useless transmission. Towing a heavy load, driving in continuous stop and go traffic in hot weather, and racing can also cause a transmission to overheat.

Finally, towing the car with the drive wheels (front or back, depending on the car) still on the road can damage a transmission as well. Your towing company should know better, but just in case, be on the safe side and check.

Even when properly cared for, however, transmissions can still break down. So, if you do notice anything amiss, get it checked out sooner rather than later.
To read more on a broad range of subjects from “How To Change A Tire” to “How To Jumpstart Your Car”, visit’s Safe Driver Resources website!


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