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Signs and Symptoms of a Defective Pump on an Automatic Transmission

Updated April 17, 2017

The pump in a transmission is used to push transmission fluid through the valve body and into the gears of the transmission.The gears, clutch plates and gear bands all need to be lubricated to allow the vehicle to switch gears smoothly. When the pump begins to fail or go bad, several signs will alert you.

Check Engine Light

One of the first signs that a transmission pump is failing occurs when the check engine light displays on the instrument panel of the vehicle. The automobile needs to be taken into a dealership that has a diagnosis scanning machine to determine what the cause is. An error code will tell the technician if the transmission pump is bad. Each manufacturer has a different error code designated for the transmission pump.

Burning Smell

When a transmission pump fails, fluid is not being pushed or pumped through the transmission. As a result, the transmission begins to overheat, burning the fluid and creating a burning smell. This odour is most prominent when you are checking the transmission fluid level with the dipstick. The transmission fluid will also be dark coloured when this overheating occurs.

Harsh Shifting

Another signal that the transmission pump is failing is if the gear lever or shift lever on a manual transmission becomes hard to shift. An automatic transmission displays harsh shifting by jerking or hesitating when the vehicle is accelerating. This harsh shifting occurs because the gears are not being lubricated.

Transmission Noise

Transmission noise is also a common symptom of a bad transmission pump. The gears and sprockets of the transmission are not being lubricated, which creates a lot of friction between parts. This results in premature wear of the parts and, eventually, gear slack, where there is more space in between the teeth of the gears. This space causes the teeth to slap together creating a loud noise during normal driving conditions.

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About the Author

Horacio Garcia has been writing since 1979, beginning his career as the spokesperson for Trinity Broadcast Network. Within 10 years Garcia was being called upon to write speeches and scripts for several state and federal congressmen, local broadcast networks and publications such as "Readers Digest." He received his bachelor's degree in public relations from Argosy University.