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Old 03-01-2016, 12:37 PM
Oscar_Ross Oscar_Ross is offline
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Smile Re: Understanding why cars dont move when engine is reving

Quote:
Originally Posted by brcidd View Post
Uhmm- Errh- That's is why there is a torque converter between engine and every automatic transmission- think of it as a fluid clutch- that only transmits torque, (or rotation) when engine rpms go up- the more power required to move the car, the faster it has to turn. When idling, the engine turns and tranny doesn't because the fluid is moving slowly in the torque converter (pump) as rpm increases so does fluid pressure and now the tranny starts to turn.

The only time the engine and tranny turn the same speed is with TCC lock-up- a solenoid allows the engine to lock onto the torque converter housing to drive both engine and tranny at same speed- this is designed for fuel economy.

Overspeed tranny means the tranny (output) is turning faster than the engine- and is achieved by using different gears in the tranny....
Thank you that makes alot of sense !!
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