Shift Solenoid - Single

Replace a faulty shift solenoid in the 8L90 8-speed automatic transmission by removing the transmission pan, valve body cover, and accessing the solenoid pack.

Warnings

Tools required

Parts

• Shift solenoid (identify which solenoid 1-6 via diagnostic code) × 1 — Use OEM GM/ACDelco solenoid for 8L90
• Transmission pan gasket × 1 — 24256991 or equivalent
• Valve body cover gasket/seal × 1 — Use OEM specification
• Transmission filter (recommended replacement) × 1 — 24278370 or equivalent
• Transmission drain plug crush washer × 1 — Use OEM specification

Fluids

• ACDelco Dexron VI ATF — 11.5 qt

Preparation

1. Obtain diagnostic trouble code (DTC) to identify which specific shift solenoid has failed (e.g., P0757 = Shift Solenoid 2)
2. Park vehicle on level surface and set parking brake firmly
3. Raise vehicle and support securely on jack stands at frame rails, providing clearance for transmission pan access
4. Allow transmission to cool completely if vehicle was recently driven (minimum 1 hour)
5. Position large drain pan under transmission pan area

Procedure

1. 1

   Drain transmission fluid
   Locate the drain plug on the bottom of the transmission pan (driver's side). Remove the drain plug and allow fluid to drain completely into the drain pan. This will take 5-10 minutes. Inspect drained fluid for metal particles or burned smell indicating additional transmission damage. Remove and discard the old crush washer from the drain plug.
2. 2

   Remove transmission pan
   Remove all transmission pan bolts in a criss-cross pattern, starting from the center and working outward. Leave two bolts at opposite corners loosely threaded. Carefully pry the pan loose and allow remaining fluid to drain. Remove final two bolts and lower the pan. Be prepared for additional fluid spillage. Inspect the pan for metal debris or sludge buildup.
3. 3

   Remove transmission filter
   The filter is held by bolts to the valve body. Remove the filter mounting bolts and carefully pull the filter straight down to remove it from the valve body. Inspect the filter for debris and damage. Note the orientation of the filter seal for reinstallation.
4. 4

   Clean pan and inspect magnet
   Thoroughly clean the transmission pan interior with brake cleaner. Remove the magnetic drain plug and wipe clean - inspect for excessive metal particles (small amount of fine metallic dust is normal). Clean all gasket material from the pan mating surface using a plastic scraper. Do not gouge the sealing surface.
5. 5

   Remove valve body cover
   Locate the valve body cover on the bottom of the valve body assembly (this is separate from the transmission pan). Remove all cover screws in a criss-cross pattern. Carefully remove the cover to expose the solenoid pack. Note the position of any check balls or small components that may be present.
   ⚠Small check balls or springs may fall out when removing the valve body cover. Note their positions carefully or reference a service diagram.
   Torque spec

   Cover Screws14 Nm (10 lb-ft)
6. 6

   Disconnect solenoid electrical connector
   Locate the internal wiring harness connector that connects to the solenoid pack. Release the connector locking tab and carefully disconnect the electrical connector from the solenoid assembly. Note the connector orientation and routing for reinstallation.
7. 7

   Remove and replace failed solenoid
   Identify the specific failed solenoid based on your diagnostic code (solenoids are numbered/labeled on the solenoid pack). Remove the bolt(s) securing the failed solenoid. Carefully pull the solenoid straight out from the valve body. Inspect the solenoid bore for debris. Lubricate the new solenoid O-rings with clean Dexron VI fluid and install the new solenoid, ensuring it seats fully. Install and torque the solenoid retaining bolt(s).
   ⚠Do not cross-thread solenoid bolts. Solenoids must be fully seated before tightening bolts or internal valve body damage may occur.
   Torque spec

   Sensor Bolts14 Nm (10 lb-ft)
8. 8

   Reinstall valve body cover
   Ensure all check balls and springs are in their correct positions (if applicable). Install a new valve body cover gasket/seal. Position the cover and install all cover screws finger-tight. Torque the cover screws in a criss-cross pattern from center outward.
   Torque spec

   Cover Screws14 Nm (10 lb-ft)
9. 9

   Install new transmission filter
   Install the new transmission filter with a new seal/O-ring. Ensure the filter is properly aligned and seated against the valve body. Install and torque the filter mounting bolts evenly.
10. 10

    Reinstall transmission pan
    Clean the transmission case pan rail thoroughly with brake cleaner. Install the new transmission pan gasket (verify gasket alignment with all bolt holes). Position the pan carefully and install all pan bolts finger-tight. Torque the pan bolts in a criss-cross pattern from the center outward to avoid gasket distortion.
    Torque spec

    Pan Bolts20 Nm (15 lb-ft)
11. 11

    Install drain plug and refill transmission
    Install a new crush washer on the drain plug and install the drain plug into the transmission pan. Torque the drain plug to specification. Locate the fill plug on the side of the transmission pan (passenger side). Remove the fill plug. Using a fluid pump, add approximately 5 quarts of Dexron VI ATF through the fill hole. This is an initial fill only.
    Torque spec

    Drain Plug42 Nm (31 lb-ft)
12. 12

    Perform fluid level check procedure
    Start the engine and allow it to idle. With the engine running and transmission in Park, continue adding fluid through the fill hole until fluid begins to drip from the fill hole. The transmission fluid temperature must be between 95-104°F (35-40°C) for proper fill level. When fluid drips steadily from the fill hole at proper temperature, install the fill plug and torque to specification. This requires a scan tool with transmission temperature monitoring capability for accuracy.
    ⚠Proper fluid level can only be verified with transmission at specific operating temperature. Use a professional scan tool to monitor transmission fluid temperature during fill procedure.
    Torque spec

    Fill Plug42 Nm (31 lb-ft)

Reassembly

1. Lower vehicle from jack stands and verify no fluid leaks from pan, drain plug, or fill plug
2. Clear any diagnostic trouble codes with a scan tool
3. Check transmission fluid level again after vehicle reaches normal operating temperature (185-194°F)

Verification

• Start the engine and verify no transmission fluid leaks while idling
• Perform a test drive including all gear ranges (Park, Reverse, Neutral, Drive, and manual shift modes if equipped)
• Verify smooth shifts and that the original diagnostic trouble code does not return
• Use a scan tool to monitor shift solenoid operation and verify the new solenoid is functioning correctly
• Recheck fluid level after test drive at proper operating temperature (transmission temp 95-104°F for level check)
• Inspect under vehicle for any fluid leaks after test drive

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