1. Identify which sensor needs replacing:
* Vehicle Speed Sensor (VSS): This sensor provides speed information to the speedometer, ABS system, and possibly the odometer. It's usually located on the differential housing (rear axle).
* Transmission Speed Sensor (TSS): This sensor provides speed information to the transmission's computer (PCM) for shifting purposes. Its location varies depending on the transmission type (e.g., 4L60E, 4L80E). It's usually near the transmission itself.
You MUST determine which sensor is faulty before proceeding. A diagnostic trouble code (DTC) read from the vehicle's computer using a scan tool is the most reliable way to pinpoint the problem. Symptoms (inaccurate speedometer, shifting problems, ABS light) can point you in the right direction, but aren't conclusive.
2. General Replacement Procedure (varies slightly depending on sensor location):
This outlines the general steps. Always consult a repair manual specific to your 1998 Chevy Suburban and its transmission type for detailed instructions and diagrams. Improper installation can lead to further damage.
* Safety First: Disconnect the negative battery cable before starting any work.
* Access the sensor: This is the most variable step. For the VSS, you'll likely need to jack up the rear end, secure it on jack stands, and possibly remove the rear wheels or parts of the exhaust system for access. For the TSS, access might involve removing the transmission pan or parts of the undercarriage shielding.
* Disconnect the electrical connector: Carefully unplug the electrical connector from the sensor.
* Remove the sensor: This usually involves unscrewing the sensor from its mounting location. It might be held in place with a bolt or a clip. Note: Sometimes the sensor can be difficult to remove due to corrosion. Use penetrating oil if needed.
* Install the new sensor: Install the new sensor, ensuring it's seated correctly. Tighten the bolt or secure the clip to the specified torque.
* Reconnect the electrical connector: Ensure the connector is securely plugged in.
* Reassemble: Reinstall any parts you removed to access the sensor.
* Lower the vehicle: Carefully lower the vehicle from the jack stands.
* Reconnect the battery: Reconnect the negative battery cable.
* Clear codes (if necessary): Using a scan tool, clear any diagnostic trouble codes related to the speed sensor. This allows the system to reset and properly recognize the new sensor.
* Test: Test drive the vehicle to verify that the speedometer, shifting, and ABS (if applicable) are functioning correctly.
Important Considerations:
* Torque Specifications: Always use the correct torque specification when tightening the sensor bolt to prevent damage. This information is found in your repair manual.
* Repair Manual: A repair manual specific to your vehicle is invaluable. It provides detailed instructions, diagrams, torque specifications, and other crucial information.
* Professional Help: If you're uncomfortable performing this repair yourself, it's best to take your Suburban to a qualified mechanic.
Remember, this is general advice. Without knowing the specific sensor and transmission type, precise instructions can't be given. Consult a repair manual for your exact vehicle to ensure a safe and successful repair.
