A GM truck that suddenly slams into gear, loses its speedometer, refuses to lock the converter, or drops into a limp second gear with a P0716, P0717, P0722 or P0723 stored is telling you it lost a speed signal. This is the GM Genuine Parts 24203876 transmission speed sensor, the same part also sold under the ACDelco OE label, and it comes with its seal. GM uses this one sensor for both input and output speed positions on its 4L60E, 4L65E, 4L70E and 4L80E family, which is why it is the most common speed sensor rebuilders keep on the shelf for Silverado, Sierra, Tahoe, Yukon, Suburban, Express and Escalade work.
What the speed sensor does in a 4L60E or 4L80E
This is a magnetic pickup. A toothed reluctor ring spins past its tip and induces a small AC signal whose frequency rises with shaft speed. The output speed sensor reads the output shaft, and the computer turns that into road speed for the speedometer, cruise control, shift timing and converter lockup. The input speed sensor reads the turbine side. By comparing the two, the computer calculates the actual gear ratio, which is how it spots slip and adjusts line pressure. Lose either signal and the computer cannot trust its own math, so it raises line pressure and changes shift strategy, which the driver feels as harsh, bangy shifts or a fail-safe gear.
Symptoms of a failing speed sensor
- Codes P0716 or P0717 (input speed sensor performance or no signal), or P0722 or P0723 (output speed sensor no signal or intermittent)
- Harsh or banging shifts that started all at once, often with a check engine light
- Speedometer that drops to zero, sweeps, or reads erratically
- No converter lockup at cruise, or the truck holding a single gear in fail-safe
- ABS or traction lights on some trucks, since the output speed signal is shared with other modules
How to confirm the sensor is bad
Most speed sensor codes on these units turn out to be circuit faults rather than a dead sensor, so test before you buy. Unplug the sensor and check the connector for oil, corrosion and bent pins. Measure sensor resistance against the service specification for your year, then watch live speed data on a scan tool while a helper rolls the truck or spins a wheel on a lift; the reading should rise smoothly with no dropouts. Pull the sensor and look at the tip for metal debris, which can mask the signal. Transmission Digest documented a 4L70E case where P0716 and P0717 came back after a repair because the input sensor wiring was not secured in its brackets on the pump and was chafed by the spinning reverse input drum, and another where the input sensor ground was lost inside the control module. Our 4L60E VSS, ISS and OSS guide walks the full test, and the 4L60E P0716 fix guide covers the input side code by code.
Fitment
The listing covers the GM 4L60E, 4L65E, 4L70E and 4L80E in Chevrolet, GMC, Buick and Cadillac trucks, vans and SUVs. Where the sensor lives depends on the unit. On the 4L80E the input and output sensors are both on the outside of the case, so this is a quick external job. On a two-wheel-drive 4L60E the output sensor threads into the tailhousing, while on four-wheel-drive trucks the vehicle speed signal is read at the transfer case instead. GM added an internal input speed sensor to the 4L60E family around 2005 and 2006; it is mounted on the pump, so replacing an input sensor on those units means removing the transmission. Because of those differences, match the number on your old sensor to 24203876 or send us the year and VIN before ordering. Browse the 4L60E parts page or the 4L80E speed sensor symptoms guide if you are working on a heavy-duty truck.
Install notes
- Clean around the sensor before removing it so dirt does not fall into the bore.
- Unplug the connector, remove the hold-down bolt and twist the sensor out. Catch any fluid that comes with it.
- Wipe the new sensor tip, lubricate the supplied seal with clean ATF, and push the sensor in by hand; do not hammer or pry it in.
- Torque the hold-down bolt to the service manual value, plug in the connector, and clear the codes. Top up with Dexron VI if fluid was lost.
- On a two-wheel-drive truck with a leaking or damaged tailhousing, a new 4L60E 2WD extension housing with seal solves both problems in one job.
Road test and watch the speed readings on the scan tool. If the shifts are still harsh with good speed data, look next at line pressure control; the 4L60E pressure control solenoid is the usual suspect.
