Identifying Transmission Problems

You probably wouldn't be reading this page if you didn't suspect that you have an automatic transmission problem. Typical problems that you may notice include: sluggish or hard shifting between gears, or maybe you hear a clinking sound when the transmission shifts gears, or you feel your vehicle shudder when the transmission shifts gears. If you are like most people, when something starts to go wrong, you naturally assume the worst … a need to rebuild or replace the transmission. But the problem may be simpler and less expensive than that. The following steps will help you determine the severity of your transmission problem. But first you need a little information about automatic transmissions:

Late model automobile transmissions include a number of integrated components: Planetary gears that allow the engine to operate in an optimal performance range at various speeds, a hydraulic system that acts as a clutch to let the engine keep running when the vehicle is at a stop, a governor and throttle cable sensor that tells the transmission when to shift gears, and an internal computer (later model vehicles) that optimizes transmission performance when you make operating choice between higher power (acceleration) and economy (better mileage). In addition, an external computer works together with a number of sensors to keep your transmission's shifting properly synchronized with the engine's performance. OK, with this background in mind let's get started:

STEP 1: Check the display lights.

Look to see if your vehicle's "check engine" light on the display panel is on. This light only indicates that there a problem has been detected by the computer. You must get a reading of the diagnostic code or codes to determine if the problem is with the engine, transmission or body.

If the "OD" light (Overdrive) light is flashing it means that the controller has identified an internal transmission problem. In either case a on-board diagnostic (OBD) tool will need to be attached to the computer port to retrieve the codes. Some mechanics charge for reading codes and some auto parts stores provide the service for free. If the code indicates an internal transmission problem you will probably need to take the vehicle to a transmission specialist. However, if the code indicates an electrical fault an external sensor or solenoid may have gone bad. In that case a mechanic may be able to replace the suspect part relatively inexpensively. If you do not have a check engine or OD light on or flashing go to step 2.

STEP 2: Check the engine idle.

With engine running and in the transmission in park put your hand on the engine cover. If possible, determine whether you have abnormal engine vibrations or a misfiring engine. You may also try slowly increasing engine rpm while the vehicle is in park to see if you can determine if your engine is running rough. If so you should have the engine tuned. Since both the engine and the transmission work together, it is possible that an out of tune engine can make the transmission seem to malfunction, even though the "check engine" light is not on. If the engine is idling or running smoothly, go to step 3.

STEP 3: Check the transmission fluid level with your dipstick

The most common problem with automatic transmission performance is low automatic transmission fluid level. For most vehicles the transmission fluid dipstick is clearly labeled "Transmission" or "Transmission Fluid". For most vehicles, check the transmission fluid while the engine is hot, and the vehicle is on level ground (look to see if the directions for checking the level are written right on your vehicle's dipstick. If not, check your owner's manual for the correct checking procedure.) Wipe the dipstick clean, insert and remove it several times, and note the fluid level. If the fluid level is in the operating range indicated on the dipstick - go to STEP 4. If it is low, in all likelihood you have a leak. Checking the pavement where you normally park your vehicle at home could show spots or pools of fluid that would also indicate a leak. In any event you should have your mechanic put the vehicle on a lift and check the transmission gaskets for evidence of leaking transmission fluid. Also ask the mechanic to check the radiator fluid for presence of automatic transmission fluid. Sometimes the ATF cooler in the radiator will start leaking and will need to be replaced.

If you determine that you have a transmission fluid leak, you will need to have a mechanic replace the leaking gasket or ATF cooler. Depending on the amount of fluid leaking, you may be able to keep adding automatic transmission fluid for a short period of time. But go ahead and schedule the repair as soon as possible since improper ATF level can result in serious damage to your transmission's internal parts. It's important to note that you must use the manufacturer's recommended automatic transmission fluid when adding fluid. You can read the specifications on the dipstick, or check your owner's manual. And take it easy when adding fluid … an overfilled transmission can create problems as well.

STEP 4: Check the transmission fluid color and smell.

Pull the transmission dipstick and place a drop of fluid from the dipstick onto a paper towel. Wait 30 seconds or so. If the spot spreads out quickly and is red or light brown in color the fluid is probably OK. But if the spot does not spread and is dark brown in color it may indicate that you transmission fluid has failed or is failing. Varnish on the dipstick that does not wipe off can also indicate failing transmission oil.

If you find any of these conditions your probably realize that you haven't been having your transmission oil replaced on a regularly scheduled basis (see owner's manual for recommended transmission oil change mileage for your vehicle). You may be tempted to go ahead and get the oil changed at a quick lube or regular mechanic. But if you've got to this point it you need to understand that the color of the oil and the contents of the transmission filter contain valuable clues that can help your transmission specialist determine the cause of your problem and you are better off skipping the oil change and going to step 5.

STEP 5: Take your vehicle to a transmission specialist.

Ok, you've eliminated the easy problems and now believe you have an internal transmission problem. You need to get the vehicle to a transmission repair specialist for professional evaluation. The most important consideration is to use someone you trust based on previous experience or the referral of friends or associates. The specialist will run through the above checks and may also test drive the vehicle. Based on his experience he should be able to give you a fairly accurate estimate on the maximum cost to repair the transmission.

If you live in the north Dallas, Texas area, including Richardson, Plano, Allen, Frisco, or McKinney, and would like us to schedule a transmission consultation, please feel free to Contact Us.