* Input Speed (for the transmission): This information is usually derived from the transmission itself, often from a sensor within the transmission case, or integrated into the transmission's output shaft. It won't be readily accessible without transmission disassembly. There isn't a single, easily identified "input speed sensor."
* Output Speed: This is typically measured by a Vehicle Speed Sensor (VSS), often located on the rear differential or on the transmission tailhousing. To pinpoint it on your specific truck, you'll need to consult a repair manual or a wiring diagram specific to your truck's year, engine, and transmission. The VSS measures the speed of the driveshaft output, effectively the vehicle speed.
To find these sensors:
1. Consult a Repair Manual: A factory service manual or a reputable aftermarket repair manual specific to your 1998 Dodge Ram 2500 with the Cummins engine and transmission will show you the exact locations. This is the most reliable method.
2. Use a Wiring Diagram: A wiring diagram will show you where the sensor wires originate. By tracing the wires, you may be able to locate the sensor.
3. Visual Inspection (Difficult and Time-Consuming): You can try visually inspecting the transmission and rear differential, but accessing these areas can be difficult and requires some mechanical knowledge. Be careful not to damage anything during your inspection.
In summary: Don't expect a simple "here it is" answer. The location requires looking at your specific truck's documentation due to variation in transmissions. Using a repair manual is highly recommended to avoid damaging components.
