What Are the Signs of a Bad Torque Converter?by TJ Hinton
Your torque converter is essentially a hydraulic pump that acts as the link between the engine and the transmission. Various components within the torque converter use vanes, similar to a turbine, to act on the transmission fluid within the unit to create a fluid coupling, as well as provide the fluid pressure that the transmission needs. Failures within the torque converter can cause symptoms similar to a failing transmission, so include it in a diagnosis of suspected transmission problems. If you have a transmission failure that released metal salt and friction-material particulates, then you should replace the torque converter as well because you can't fully flush out the debris. The torque converter is a sealed unit, and as such must be serviced or replaced as a unit. The unit is encased in a shell made of two halves that are welded together. Failures of the welds in the outer or inner joint will cause a fluid leak.
Your torque converter can make a variety of noises when it goes bad. You may first notice a whine, similar to a power-steering pump that is low on fluid. The stator within the assembly uses an overrun mechanism with a series of clutches that, when bad, can cause a rattling noise. The noise may be light while idling in park, but when you put the transmission in gear, the sound will increase in volume and frequency, and that is the death knell of your converter.
Slippage and Weak Acceleration
As the output pressure from the torque converter drops, the transmission will be starved and start to slip. This may manifest itself as a general loss of power when driving, especially when accelerating. Address this as soon as possible to prevent prematurely wearing out the friction material in the transmission. Slippage can also occur if the converter clutch fails to engage fully, leaving only the fluid-coupling effect, which is inherently inefficient.
Another symptom of lowered pressure output from the converter is a tendency to have soft, or delayed shifts. You will lose the nice, crisp feeling of the transmission shifting and engaging properly. You may find that increasing the output pressure from the converter by raising the engine rpm a bit will help the transmission shift into gear, and also to engage when starting from a stop.
Inconsistent output from the torque converter can cause the transmission to increase and decrease the vehicle speed with no concurrent change in throttle as the hydraulic pressure varies. This can present a dangerous driving condition, and you shouldn't drive the vehicle until repairs are performed. Sometimes this variation can feel like a shudder, though you should inspect the transmission mounts and repair or tighten them as necessary before looking to the torque converter.
TJ Hinton trained as an auto mechanic at Mississippi Gulf Coast Community College and then later graduated from MMI as a certified motorcycle mechanic . He's also worked for 20+ years in home construction, remodeling and repair. His articles appear on InternetAutoGuide.com and TopSpeed.com.