A lock-up torque converter, also known as a torque converter clutch, is a part of the transmission mainly found in late-model automatic vehicles. Lockups serve to improve efficiency by setting the torque converter at certain levels of output. They are also designed to help improve fuel economy. Although they have their advantages, they can have their share of problems at times. There are many symptoms that indicate whether the torque converter lock-up is going bad.
A sign that the torque converter lock-up is failing is slippage between gears. The converter will be unable to hold its position, engaging in different driving ranges randomly. The vehicle will also tend to rev up and down as the torque converter engages or disengages, unable to keep the lock-up clutch in place. This is often confused with low fluid levels and can cause permanent damage to the torque converter as a whole. Fuel economy drops as well when the lock-up torque converter slips from one gear to another at random.
One of the main symptoms of a bad lock-up torque converter is engine shuddering. This often happens when the lock-up fails to release properly or on time when shifting, in which case the engine will shudder and die when the vehicle comes to a stop. In some cases, the lock-up will fail to engage altogether. At this point, the car will no longer be drivable because of constant stalling.
As the vehicle slows down, it will fail to downshift if the lock-up converter is bad. The driver may notice that during acceleration, the revolutions per minute are low enough that the vehicle will have difficulty moving quickly. In some cases, the converter lock-up will attempt to keep the vehicle moving until it comes to a stop, where it may stall and die.