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Torque converter problems can feel like transmission problems, and transmission problems can feel like converter problems. The best diagnosis starts with the symptom, when it occurs, and what changed before it began.
Common Torque Converter Symptoms
Common complaints include shudder, vibration, excessive heat, poor acceleration, inconsistent stall, delayed engagement, lockup problems, unusual noise, or engine RPM that rises without corresponding vehicle speed.
Shudder or Vibration
Shudder can occur during lockup engagement, light-throttle cruising, or acceleration. Possible causes include converter clutch problems, contaminated fluid, driveline vibration, engine misfire, or transmission control issues. Note the speed, gear, throttle position, and temperature when the shudder occurs.
Excessive Heat
Heat is one of the biggest enemies of automatic transmissions and converters. Excessive converter slip, heavy towing, inadequate cooling, incorrect gearing, or a converter that is poorly matched to the combination can all increase temperature.
Stall Speed Feels Wrong
If the converter seems to stall too low or too high, compare the current vehicle combination with what the converter was originally selected for. Engine torque, camshaft, boost, vehicle weight, tire diameter, and rear gearing can all change how the same converter behaves.
Lockup Problems
A lockup converter that fails to lock, locks too early, or repeatedly cycles in and out of lockup can create heat and drivability complaints. Electrical controls, tuning, hydraulic pressure, and the converter clutch itself may all be involved.
Noise From the Converter Area
Metallic noise, rattling, scraping, or grinding should be investigated quickly. Flexplate damage, loose converter bolts, pump issues, bearing problems, or internal converter damage can produce similar sounds.
What Information Helps Diagnosis
Have the vehicle year, engine, transmission, converter part number, rear gear, tire size, approximate horsepower, intended use, fluid condition, temperatures, and a description of the symptom ready. The more complete the information, the easier it is to narrow down the cause.
Repair, Rebuild, or Replace?
Not every converter problem requires a new converter. Depending on condition and application, inspection, rebuilding, lockup repair, or a stall change may be possible. If the vehicle combination has changed substantially, a new converter may be the better answer.
Use the complete vehicle combination. Engine torque, camshaft, transmission, vehicle weight, rear gearing, tire diameter, power adders, and intended use can all change how a converter behaves.
Need Help Choosing or Diagnosing a Converter?
Have a converter problem you can’t pin down? Start a Boss Hog repair request and tell us exactly what the vehicle is doing.
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Technical information is provided as a general guide. Final torque converter selection should be based on the complete vehicle combination and intended use.