Transmission Speed Sensor - Output

This procedure covers the replacement of the output speed sensor on the automatic or manual transmission of a 2007 Ram 3500 with the 5.9L Cummins diesel engine.

Warnings

Tools required

Parts

• Transmission output speed sensor × 1 — Use OEM Mopar specification for 48RE/G56 transmission
• O-ring seal for speed sensor × 1 — Often included with sensor, verify before installation

Fluids

• ATF+4 — 1 qt

Preparation

1. Park vehicle on level ground and engage parking brake
2. Chock the front wheels securely
3. Raise rear of vehicle and support on jack stands rated for vehicle weight
4. Allow transmission to cool to ambient temperature if vehicle was recently operated
5. Position drain pan under transmission tail housing area to catch fluid
6. Locate the output speed sensor on the driver side of the transmission tail housing

Procedure

1. 1

   Access the output speed sensor
   From underneath the vehicle, locate the output speed sensor on the 48RE transmission near the rear extension (tail) housing at the output shaft area. Verify the exact location and orientation against the service manual before proceeding. Clean the area around the sensor with a wire brush to remove any dirt or debris that could fall into the transmission during removal.
2. 2

   Disconnect electrical connector
   Locate the electrical connector attached to the output speed sensor. Press the locking tab on the connector and carefully pull the connector straight off the sensor. If the connector is difficult to remove, use a flathead screwdriver to gently release the locking tab while pulling. Inspect the connector terminals for corrosion or damage.
3. 3

   Remove the speed sensor mounting bolt
   Using a 10mm socket and ratchet, remove the bolt securing the speed sensor to the transmission case. On the 48RE, the sensor is retained by a single hold-down bolt. Remove this bolt to free the sensor. Keep the mounting bolt in a safe location for reinstallation.
4. 4

   Extract the speed sensor
   Carefully pull the output speed sensor straight out of the transmission case. You may need to twist slightly while pulling to break the O-ring seal. Be prepared for transmission fluid to drain from the sensor bore. Allow fluid to drain into the catch pan. If the sensor is stuck, use a gentle twisting motion but do not pry against the transmission case.
5. 5

   Inspect the sensor bore and O-ring
   Once the sensor is removed, inspect the bore in the transmission case for debris, metal shavings, or damage. Wipe the area clean with a shop towel. Inspect the old sensor O-ring for damage or deterioration. Check inside the bore to ensure the old O-ring did not remain in the transmission case.
6. 6

   Prepare the new sensor
   Remove the new output speed sensor from its packaging and verify it matches the old sensor in physical appearance and connector type. Install the new O-ring onto the new sensor if it is not pre-installed. Lightly coat the O-ring with clean transmission fluid appropriate to the unit (ATF+4 for the 48RE automatic) to aid installation and create a proper seal.
7. 7

   Install the new speed sensor
   Carefully insert the new output speed sensor into the transmission case bore, ensuring the O-ring does not roll or become pinched. Push the sensor firmly into place until it seats fully against the transmission case. The sensor should sit flush with the mounting surface.
8. 8

   Secure the sensor and reconnect electrical
   Install the mounting bolt and tighten by hand first to ensure proper thread engagement. Torque the hold-down bolt to approximately 21 ft-lbs (28 Nm) per Mopar specification — verify the exact value in the service manual and do not overtighten. Reconnect the electrical connector to the sensor, ensuring it clicks into place and the locking tab engages fully.
9. 9

   Check and refill transmission fluid
   Lower the vehicle to the ground. Check the 48RE automatic transmission fluid level using the dipstick and add ATF+4 fluid as necessary to bring the level to the proper range. (For the G56 manual, use only the manufacturer-specified manual transmission fluid — NOT ATF+4.) Start the engine and cycle through all gear positions, then recheck fluid level with engine running and transmission at operating temperature.

Reassembly

1. Ensure the sensor electrical connector is fully seated and locked
2. Verify no tools or parts were left under the vehicle
3. Remove jack stands and lower vehicle completely to the ground
4. Properly dispose of any spilled transmission fluid

Verification

• Start the engine and verify no warning lights are illuminated on the instrument cluster
• Check for transmission fluid leaks around the speed sensor installation area while engine is running
• Test drive the vehicle and verify the speedometer operates correctly
• Verify the transmission shifts properly through all gears
• Use a diagnostic scan tool to confirm the transmission output speed sensor is reporting data to the PCM with no diagnostic trouble codes present

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

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