Title.
When a car has its engine on, the engine is working. But if its in park, the car doesn’t move. How? The engine is still running like if the car was driving, but what mechanism prevents the car from moving?
In: 0
On an automatic car, once you shift into park or neutral, every clutch inside the transmission disconnects, so the engine/flywheel/torque converter output shaft turns nothing. Plus the parking pawl locks the output shaft of the transmission to prevent the car from moving.
For stopping at a red light shifted into Drive, the transmission is in gear so any transmission input shaft rotation will result in car rolling forward. At this time the slipping part is the “torque converter” upstream of the transmission.
Torque converter takes the role of the foot operated clutch and lower gear ratios on an automatic car. If you hold the car still while in gear, the converter slips so the engine can keep turning without moving the car even if you are in gear.
On older generation cars, the TC is always slipping because it’s a fluid coupling. This creates heat and fuel efficiency problems. Newer cars will lock up the TC once you are speeding up eliminating this friction loss.
Latest Answers