Transmission Speed Sensor - Output

Replace the transmission output speed sensor on a 2008 Dodge Viper with 8.4L V10 and 6-speed manual transmission, requiring access from underneath the vehicle.

Warnings

Tools required

Parts

• Transmission output speed sensor × 1 — Mopar 5080221AA or equivalent
• O-ring seal for speed sensor × 1 — Usually included with sensor

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow transmission to cool to safe working temperature if recently driven
3. Raise vehicle using lift or jack and secure on jack stands at manufacturer-specified lift points
4. Ensure adequate working clearance underneath vehicle

Procedure

1. 1

   Locate transmission output speed sensor
   Position yourself under the rear of the transmission. The output speed sensor is mounted on the driver's side rear section of the transmission case, near the tailhousing. It is a cylindrical sensor with a single electrical connector on top. The sensor threads directly into the transmission case.
2. 2

   Disconnect electrical connector
   Locate the electrical connector on top of the output speed sensor. Press the locking tab on the connector and pull straight up to disconnect. If the connector is tight or corroded, gently work it side to side while pulling. Avoid pulling on the wiring harness itself.
3. 3

   Position drain pan
   Place a small drain pan directly beneath the output speed sensor. When the sensor is removed, a small amount of transmission fluid (typically 2-4 ounces) will drain from the opening. Position the pan to catch this fluid.
4. 4

   Remove output speed sensor
   Using the appropriate socket or wrench (verify exact size), rotate the sensor counterclockwise to unthread it from the transmission case. The sensor should turn relatively easily. Once loose, unscrew it by hand and withdraw it from the transmission. Allow residual fluid to drain into the pan. Inspect the sensor for damage, metal debris on the magnetic tip, or damaged O-ring seal.
5. 5

   Clean sensor mounting bore
   Using shop towels and optionally a wire brush, clean the sensor mounting bore in the transmission case. Remove any debris, old seal material, or metal particles. Wipe the threads clean. Inspect the threads inside the transmission case for damage or stripped areas.
6. 6

   Prepare new sensor
   Remove the new output speed sensor from packaging. Verify the new O-ring seal is properly seated in the groove on the sensor body. The O-ring should be clean and free of damage. Lightly lubricate the O-ring with clean transmission fluid to ease installation. If the new sensor did not include an O-ring, transfer the new O-ring from the parts kit.
7. 7

   Install new output speed sensor
   Thread the new sensor into the transmission case by hand, rotating clockwise. Ensure it threads in smoothly without cross-threading. Once hand-tight, use the appropriate socket and torque wrench to tighten the sensor to the manufacturer-specified torque (verify exact spec — commonly in the 7-9 lb-ft range for speed sensors). Do not overtighten, as this can damage the sensor body or transmission case threads.
8. 8

   Reconnect electrical connector
   Clean the electrical connector terminals with electrical contact cleaner if corrosion is present. Push the connector firmly onto the sensor until the locking tab clicks into place. Tug gently on the connector to verify it is securely locked.
9. 9

   Check transmission fluid level
   Lower the vehicle to the ground. With the transmission cold, remove the fill plug on the driver's side of the transmission case (located mid-case). The fluid level should be at the bottom of the fill plug hole. If fluid was lost during sensor replacement, add the manufacturer-specified manual transmission fluid (verify exact spec for the 2008 Viper Tremec transmission — commonly a synthetic MTL/ATF+4 type) as needed until fluid begins to seep from the fill hole. Reinstall and tighten the fill plug.

Reassembly

1. Verify electrical connector is fully seated and locked
2. Confirm no transmission fluid leaks are present at sensor location
3. Lower vehicle safely from lift or jack stands

Verification

• Start the engine and verify no warning lights related to transmission speed sensor are illuminated on the instrument cluster
• Test drive the vehicle and confirm speedometer operates correctly
• Monitor for any transmission-related fault codes using a scan tool if available
• After test drive, re-inspect the sensor area for any signs of fluid leakage
• Verify transmission shifts normally through all gears

Related trouble codes on this vehicle

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