This procedure covers the removal and replacement of the input speed sensor on the 8L90 automatic transmission in 2014-2018 Chevrolet Silverado 1500 with 5.3L V8 engine.

Warnings

Tools required

Parts

• Transmission input speed sensor × 1 — ACDelco 24271579 or equivalent
• Input speed sensor O-ring seal × 1 — Usually included with sensor
• Transmission fluid (if significant loss occurs) × 1 — ACDelco Dexron VI

Fluids

• ACDelco Dexron VI ATF — 1 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow transmission to cool if vehicle was recently operated (fluid can be hot)
3. Raise front of vehicle and support securely on jack stands rated for vehicle weight
4. Remove driver side front wheel for improved access (optional but recommended)
5. Locate input speed sensor on driver side of transmission case approximately 6 inches behind bellhousing

Procedure

1. 1

   Disconnect electrical connector
   Locate the electrical connector on the input speed sensor. Press down on the locking tab and pull the connector straight off the sensor. Inspect connector terminals for corrosion or damage. Clean terminals with electrical contact cleaner if necessary.
2. 2

   Position drain pan
   Place a drain pan directly under the input speed sensor location. Expect approximately 0.5-1.0 quart of transmission fluid to drain when sensor is removed. Position pan to catch fluid that may run down the transmission case.
3. 3

   Remove sensor mounting bolt
   Using a 10mm socket with extension, remove the single bolt securing the input speed sensor to the transmission case. The bolt may have a small amount of threadlocker applied. Keep bolt for reinstallation if in good condition.
   ℹ️Some fluid seepage may begin as bolt is loosened.
4. 4

   Extract speed sensor
   Carefully pull the input speed sensor straight out from the transmission case bore. Avoid twisting or rocking the sensor excessively to prevent damage to the bore. Fluid will flow from the opening once sensor is removed. Allow fluid to drain into pan.
5. 5

   Inspect and clean bore
   Once fluid drainage slows, inspect the sensor bore in the transmission case for debris or metal shavings. Wipe the mounting surface clean with a shop towel. Check the old sensor O-ring to ensure it came out with the sensor and is not stuck in the bore. Use a pick tool to remove old O-ring if necessary.
   ⚠Do not allow dirt or debris to enter the transmission case opening.
6. 6

   Prepare new sensor
   Remove new input speed sensor from packaging. Verify new O-ring seal is installed on the sensor body. Lightly lubricate the O-ring with clean Dexron VI ATF to ease installation and prevent O-ring damage. Do not use petroleum-based lubricants.
7. 7

   Install new sensor
   Align the new input speed sensor with the bore in the transmission case. The sensor will only install in one orientation due to the keyed design. Push the sensor straight into the bore until it is fully seated and flush with the mounting surface. Ensure sensor does not cock or bind during installation.
   ⚠Do not force sensor. If resistance is felt, remove and check for proper O-ring placement and bore cleanliness.
8. 8

   Install and torque mounting bolt
   Thread the sensor mounting bolt in by hand to ensure proper thread engagement. Once snug, torque the bolt to specification using a torque wrench. Do not overtighten as this can damage the sensor housing or transmission case threads.
   Torque spec

   Sensor Bolts14 Nm (10 lb-ft)
9. 9

   Reconnect electrical connector
   Push the electrical connector onto the new sensor until a positive click is heard or felt, indicating the locking tab has engaged. Gently pull on the connector to verify it is secured. Ensure connector boot is properly seated to prevent moisture intrusion.
10. 10

    Check and add transmission fluid
    Remove the transmission fill plug using 13mm socket. With engine off, add replacement Dexron VI ATF to compensate for fluid lost during sensor removal (typically 0.5-1.0 quart). Reinstall fill plug and torque to specification.
    ℹ️Final fluid level check must be performed with engine running at operating temperature per manufacturer procedure.
    Torque spec

    Fill Plug42 Nm (31 lb-ft)

Reassembly

1. Reinstall driver side front wheel if removed, torque lug nuts to 140 lb-ft in star pattern
2. Lower vehicle from jack stands
3. Perform final transmission fluid level check with vehicle on level ground, engine running at idle, and transmission at normal operating temperature (approximately 180-200°F)
4. Add fluid as necessary to bring level to proper range on dipstick or fill plug level

Verification

• Start engine and verify no transmission fluid leaks at sensor location
• Connect scan tool and verify input speed sensor signal is present and reading correctly (should show 0 RPM at idle in Park)
• Test drive vehicle and verify transmission shifts normally through all gears
• Verify no transmission-related diagnostic trouble codes (DTCs) are present, specifically P0715 (Input/Turbine Speed Sensor Circuit)
• Re-check fluid level after test drive and top off if necessary
• Inspect sensor area for any signs of fluid seepage after test drive

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