A torque converter is one of the most important parts of your automatic transmission. It is what transfers energy from the engine to the transmission. In a manual, this is done with the clutch, but in an automatic, you need something that is going to disengage the clutches when power is not being delivered to the wheels. This is where a torque converter works. Thanks to the design a torque converter can disconnect power between the engine and transmission on its own and keep your parts from getting damaged.
Input into the torque converter comes from the engine and flexplate. The flexplate, for those who are not familiar, does the same job and has the same location as the flywheel on a manual transmission. After the flex plate, energy is sent to the torque converter through the input shaft.
Transferring the Energy
After the input shaft comes to the impeller. This is similar to a fan or turbine and will push transmission fluid towards the rear of the torque converter. As this fluid flows through the torque converter, it will reach the turbine. This turbine is connected to the transmission’s input shaft. As the turbine spins, so does the input shaft which drives the transmission. If you apply the brakes when it is in park, then the turbine will simply stop spinning.
If you are sitting there thinking that this sounds horribly inefficient, you are not wrong. This is why torque converters have a stall speed. This is not actually stalling like in a manual but is what happens when the torque converter locks up. This allows a direct, mechanical, linkage from the engine to the transmission similar to a clutch.
Rebuilding a torque converter is not a difficult job, but you will need a shop manual and a torque converter parts supplier. Torque converters are expensive, so rebuilding one is a great way to save money if you have the skills to do it.