transmission

Transmission Speed Sensor - Input

for 2002 Dodge Viper 8.0L V10 · RWD

Difficulty

Moderate

Time

1.4 h

Tools

Steps

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Replacement of the input speed sensor on the Borg-Warner T56 6-speed manual transmission, requiring access from underneath the vehicle.

Warnings

⚠️Always use jack stands rated for the vehicle weight. Never work under a vehicle supported only by a floor jack.

⚠The transmission will be hot if the vehicle has been recently driven. Allow sufficient cooling time before beginning work.

⚠Transmission fluid may drain from the sensor opening. Have a drain pan positioned to catch fluid.

ℹ️The 1992 Viper uses a Borg-Warner T56 6-speed manual transmission. The input speed sensor is located on the driver's side of the transmission case.

Tools required

Floor jack and jack stands (rated for vehicle weight)Essential

Wheel chocksEssential

10mm socket and ratchetEssential

Small flat-blade screwdriver or trim toolEssential

Shop towels or ragsEssential

Drain pan (small capacity for fluid capture)Essential

Torque wrench (10-15 Nm range)Essential

Wire brush (for cleaning sensor mounting area)

Electrical contact cleaner

Inspection mirror

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Parts

Input speed sensor (VSS) × 1 — Mopar 04799109AB or equivalent
O-ring seal for sensor × 1 — Often included with sensor

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Fluids

transmission_manual — 0.5 qt

Preparation

Park vehicle on a level surface and engage parking brake firmly
Place wheel chocks behind rear wheels
Allow transmission to cool if vehicle has been driven recently (minimum 30 minutes)
Disconnect negative battery cable to prevent electrical faults during sensor replacement
Raise front of vehicle using floor jack and support securely on jack stands at manufacturer-specified jacking points
Verify vehicle is stable before working underneath

Procedure

1
Access the transmission from underneath
Position yourself under the vehicle with adequate lighting. Locate the input speed sensor on the driver's side of the T56 transmission case, approximately mid-way along the transmission housing. The sensor will have an electrical connector and is secured with a single bolt. Use an inspection mirror if needed to confirm sensor location before proceeding.
2
Disconnect the electrical connector
Locate the electrical connector attached to the input speed sensor. Press the tab or release mechanism on the connector (typically a squeeze-tab design) and pull the connector straight away from the sensor. Do not pull on the wiring harness itself. If the connector is difficult to release, use a small flat-blade screwdriver to gently depress the locking tab while pulling the connector.
3
Position drain pan
Place a small drain pan directly below the input speed sensor location. Expect approximately 4-8 ounces of transmission fluid to drain when the sensor is removed. The fluid level in the T56 is below the sensor opening when properly filled, but some fluid will escape due to internal pressure and residual fluid around the sensor cavity.
4
Remove sensor retaining bolt
Using a 10mm socket and ratchet, remove the single bolt securing the input speed sensor to the transmission case. The bolt threads directly into the transmission housing. Keep the bolt for inspection and potential reuse if not corroded or damaged.
Torque spec
Sensor Bolts11 Nm (8 lb-ft)
5
Extract the sensor
Carefully pull the input speed sensor straight out from the transmission case. The sensor has an O-ring seal that may cause slight resistance. Twist the sensor gently while pulling if necessary to break the O-ring seal. Once removed, allow any residual fluid to drain into the pan. Do not pry against the transmission case as this may damage the sealing surface.
6
Inspect and clean the mounting bore
Examine the sensor mounting bore in the transmission case for debris, metal shavings, or damaged threads. Use a wire brush to clean the bolt threads in the case. Wipe the sealing surface around the bore with a clean shop towel. Inspect the old sensor for metal debris on the magnetic tip, which is normal but excessive buildup may indicate internal transmission wear. Check the condition of the retaining bolt threads.
7
Prepare the new sensor
Remove the new input speed sensor from its packaging. Verify that a new O-ring seal is installed on the sensor body. If the O-ring is not pre-installed, carefully roll the new O-ring onto the sensor groove. Lightly lubricate the O-ring with clean transmission fluid to ease installation and prevent O-ring damage during insertion. Do not use petroleum-based lubricants.
8
Install the new sensor
Align the new input speed sensor with the mounting bore in the transmission case. Push the sensor straight into the bore until it seats fully against the transmission housing. The O-ring should compress and the sensor mounting flange should be flush with the case surface. Do not force the sensor; if resistance is encountered, remove and verify proper O-ring placement and bore cleanliness.
Torque spec
Sensor Bolts11 Nm (8 lb-ft)
9
Install and torque the retaining bolt
Insert the sensor retaining bolt through the sensor flange and thread it into the transmission case by hand. Ensure the bolt threads engage smoothly without cross-threading. Using a torque wrench and 10mm socket, tighten the bolt to 11 Nm (8 lb-ft). Do not overtighten, as this may crack the sensor housing or damage the transmission case threads.
Torque spec
Sensor Bolts11 Nm (8 lb-ft)
10
Reconnect the electrical connector
Clean the electrical connector terminals with electrical contact cleaner if necessary. Align the connector with the sensor terminals and push firmly until the locking tab clicks into place. Tug gently on the connector to verify it is fully seated and locked. Ensure the wiring harness is routed away from hot exhaust components and sharp edges.
11
Check and top off transmission fluid
Locate the transmission fill plug on the driver's side of the transmission case. Remove the fill plug using the appropriate tool. The fluid level should be at the bottom of the fill plug hole. Add Mopar MS-9224 or 75W-90 GL-4 gear oil as needed to bring the level to the fill plug opening. Reinstall the fill plug and torque to specification. Account for the small amount of fluid lost during sensor removal (approximately 0.5 quart maximum).
Torque spec
Fill Plug34 Nm (25 lb-ft)
12
Reconnect battery and lower vehicle
Reconnect the negative battery cable and tighten the terminal clamp securely. Remove jack stands and carefully lower the vehicle to the ground. Remove wheel chocks.

Reassembly

Reassembly is completed as part of the installation steps above
Ensure all electrical connections are secure and properly locked
Verify transmission fluid level is correct at the fill plug opening
Confirm no fluid leaks are present around the sensor mounting area

Verification

Start the engine and allow it to idle. Check for fluid leaks around the input speed sensor mounting area
With the engine running and transmission in neutral, verify that the speedometer is functioning (may require a short test drive)
Using a scan tool if available, monitor input speed sensor signal to confirm proper operation and signal output
Test drive the vehicle at various speeds to verify speedometer accuracy and proper transmission operation
Check for diagnostic trouble codes related to the speed sensor; clear any codes that were set prior to repair
Recheck transmission fluid level after test drive and top off if necessary