Friday, May 2, 2014
What Causes a Lock Up Torque Converter in the Transmission
Theres nothing wrong with a locked-up torque converter; as a matter of fact, lock-up torque converters have been making automatic transmissions more efficient for decades. Youll only encounter brief periods during your driving cycle where converter lock-up is not beneficial.
Converter Operation
Torque converters are fluid couplers. A turbine fan attached to the outer case (which is bolted to the engine) pushes transmission fluid through a matching turbine on the transmission input shaft. The engine doesnt push enough fluid when idling to engage the transmission turbine. As rpm rises, that fluid will begin to push against and spin the transmission-side turbine, engaging it and moving the car.
The Problem
Because there was no direct connection between the engine and transmission, a non-lock-up converter will always get worse fuel mileage than a manual transmission, which uses a clutch.
Lock-Up Function
A lock-up converter uses a clutch pack very similar to those inside the transmission itself to lock the converter case to the transmission input shaft. At about 25 mph, the computer sends a signal to an electronic actuator inside the transmission to engage the clutch pack and lock the drive line together.
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