Signs of a Bad Transmission on a Car at 40 MPH

by Michael Davidson
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A car's transmission is vital for the car to function properly. Transmissions are important because they control the engine's RPMs to ensure that the engine isn't overexerting itself while accelerating. A healthy transmission is necessary to keep an engine running at optimal performance, and when a transmission starts to fail, there are immediate effects on the car. If you're driving 40 miles per hour and think the transmission might be going bad, check for these several symptoms.


A bad transmission often will kick violently when trying to change gears. As the car approaches 40 mph, the RPMs will increase in the engine. When the transmission shifts, engine noise usually will quiet down, and the RPMs will drop. At that moment, a bad transmission can cause the car to jerk, and that could be accompanied by a loud "slamming" noise. This generally will happen at the same speed with consistency as the transmission continues to corrode.

Loss of Speed

The transmission sometimes can prevent the car from maintaining proper speed. If the car is traveling 40 mph and the speed suddenly falls while the engine continues to rev, the transmission probably is to blame, especially if pushing the accelerator has no effect and the car continues to slow down. This can be a chronic problem, or it can only last a few seconds before the transmission works properly again. If it happens once, it is likely to happen again, and the car should be serviced before the transmission is damaged further by wear and tear.

Inability to Accelerate

If your car is moving at 40 mph but is unable to accelerate any further, the transmission probably needs service or replacement. This problem can develop at any speed, depending on which gear of the transmission is going bad. The engine will continue to rev as the car tries to accelerate above that speed, but the car will not be able to shift into gear for further speed. Continuing attempts to accelerate can result in severe engine damage. The car likely would still run fine at lower speeds, but it should be taken to a mechanic immediately.

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