1999 Dodge Truck lock up torque

The torque converter will unlock at wide-open-throttle and at minimum throttle. A dropout from the throttle position sensor can happen so fast that it doesn't set a fault code, but it's enough to command the converter to unlock. Try a new throttle position sensor.

If your transmission uses a throttle cable, it could be slightly mis-adjusted, although it would act up much more often. Engine rpm is one of the enabling conditions for converter lockup. At lockup around 40 mph, engine rpm could drop too low. Converter unlocks, ... Rpm goes up, ... Lockup occurs. This problem occurs around 40 - 50 mph. The throttle position sensor problem occurs based on throttle position, not engine load or vehicle speed.

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