Buy Chevrolet G10 Speed Sensors

A speed sensor-also called a vehicle speed sensor (VSS), output-shaft sensor, transmission speed sender, or simply speed pickup-is a small magnetic or Hall-effect device that counts pulses from a toothed ring on the tail of the transmission. In every Chevrolet G10 van (roughly 1971-1995), that signal feeds the engine computer, the cruise-control module, the anti-lock-brake controller, the speedometer, and even the shift logic inside the 4L60-E automatic. When the sensor fails, the van can lose its speedometer, shift harshly or not at all, trigger a "Code 24," and switch off cruise control. (YourMechanic)

• Live speed data - The sensor's AC or digital pulse train lets the electronic control module (ECM) calculate ground speed and tailor fuel delivery, spark timing, and overdrive lock-up. (RepairPal.com)
• Gauge drive - Since 1990 the G-series abandoned a cable; the cluster gets its reading from the VSS through a buffer box mounted above the parking-brake bracket. (JustAnswer)
• ABS & Traction Aid - Wheel-speed information allows the anti-lock system to release and re-apply brake pressure, preventing skids. (NHTSA)
• Cruise & Speed Limiting - Cruise control disengages if the ECM loses a clean VSS feed, and factory speed-limit functions also depend on that signal. (HowStuffWorks)

On every fuel-injected G10 (1987-1995), the VSS threads into the tail housing of the 700-R4/4L60-E transmission, just ahead of the driveshaft yoke. Older carbureted vans (pre-1986) used a mechanical cable instead. The plastic buffer box lives on the left kick panel beside the emergency-brake pedal. (Charm Li, JustAnswer)

• Speedometer drops to zero or jumps. (Chevrolet Forum)
• Transmission holds first or second gear, or shifts late and harsh. (CarParts)
• Cruise control will not set. (JustAnswer)
• ABS warning lamp comes on during low-speed stops (shared rear-axle sensor circuit). (HowStuffWorks)
• Check-engine light with "VSS open/no activity" diagnostic trouble code. (RepairPal.com)

1. Visual check - Look for torn wiring or rust where the sensor threads in.
2. Static resistance test - Unplug the two-pin connector and measure across the sensor. A good G-van VSS sits near 1.1 k? at room temperature. (Chevrolet Forum)
3. Dynamic AC test - Spin a rear wheel with the van safely lifted; the meter should generate at least 0.5 VAC. (YouTube)
4. Scope or scanner - Back-probe the signal wire: clean square (Hall) or sine (magnetic) pulses should rise with wheel speed. (YouTube)

• Prep - Soak the mounting boss with penetrating oil if corroded; some owners report the plastic body sticks in the aluminum tail housing. (Allpar)
• Torque - Thread the new sensor finger-tight plus 1/8 turn (about 18 in-lb) to seal the O-ring without cracking the housing.
• Buffer reset - If your dash still reads zero after a new VSS, inspect or replace the speed-sensor buffer module on the kick panel. (JustAnswer)

• Anti-lock brakes - Rear-axle speed sensing began in 1990; loss of data disables ABS self-test. (HowStuffWorks)
• Traction control - While not fitted to the G10, modern ETC and traction systems also reference VSS for wheel-slip logic. (HowStuffWorks)
• Speedometer design - Electronic clusters count 40,000 pulses per mile from the sensor to move the pointer and odometer. (HowStuffWorks)

Keeping the tail-housing seal clean, routing the harness away from the exhaust, and replacing the drivetrain ground strap all help the sensor last longer. Periodically clear mud off the harness and ensure the loom clips stay tight to avoid signal drop-outs. (HowStuffWorks)

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(The early carbureted G10 used a mechanical cable, so no electronic VSS prior to the 1987 model year changeover.) (Charm Li)

Q: What tools do I need to swap the sensor?
A: An 18 mm box wrench, a flat screwdriver for the harness clip, and a small drain pan in case a few drops of ATF seep out. (Chevrolet Forum)

Q: Will a bad speed sensor damage my transmission?
A: Driving for long periods without the VSS can overheat fluid because the torque-converter lock-up never engages; fix the fault promptly. (YourMechanic)

Q: Can I clean the sensor instead of replacing it?
A: Yes-lightly brush off metal filings from the magnetic tip and reinstall with a new O-ring if the coil tests good. (YouTube)

Q: Why did my ABS light come on after the speedometer failed?
A: The computer cross-checks rear-axle speed; when the signal drops out, it disables ABS for safety and turns on the warning lamp. (HowStuffWorks)

Q: What ohm reading tells me the sensor is healthy?
A: Around 1,050-1,150 ? at 68 °F (20 °C) is typical for a G-series van magnetic sender. (Chevrolet Forum)

Q: Does the buffer box need programming after a sensor change?
A: No. It's a passive divider that simply squares up the signal; if it fails, swap it-no calibration needed. (JustAnswer)

Q: Are wheel speed sensors the same as the VSS?
A: They both read rotation, but the G10's rear-axle sensor feeds ABS only, while the VSS on the transmission feeds the engine computer and cluster. (NHTSA)

Q: How many pulses per mile does the ECM expect?
A: Forty thousand; the buffer then scales that to 2,000 ppm for the speedometer. (HowStuffWorks)

Q: Can I drive if only my speedometer is dead?
A: The van will run, but you'll lack accurate speed, overdrive lock-up, and cruise-so fuel economy and safety may suffer. Fixing the sensor restores all of those functions. (RepairPal.com)