Shift Solenoids - All

Complete replacement of all transmission shift solenoids in the 8L90 8-speed automatic transmission, requiring transmission pan removal and valve body partial disassembly.

Warnings

Tools required

Parts

• Transmission pan gasket × 1 — ACDelco 24282916 or equivalent
• 1-2-3-4 shift solenoid × 1 — ACDelco 24275875 or equivalent
• 5-6-7-8 shift solenoid × 1 — ACDelco 24275876 or equivalent
• Pressure control solenoid (1-2) × 2 — ACDelco 24275877 or equivalent
• TCC (Torque Converter Clutch) solenoid × 1 — ACDelco 24282915 or equivalent
• Valve body separator plate gasket set × 1 — Use OEM specification
• Transmission filter × 1 — ACDelco 24278243 or equivalent
• Transmission drain plug washer × 1 — Use new crush washer
• Brake cleaner (non-chlorinated) × 1 — Use OEM specification
• RTV silicone sealant (if specified by gasket) × 1 — ACDelco or equivalent (check gasket instructions)

Fluids

• ACDelco Dexron VI ATF — 11.5 qt

Preparation

1. Park vehicle on level ground and engage parking brake firmly
2. Allow transmission to cool completely (minimum 2 hours after last operation)
3. Disconnect negative battery cable to prevent electrical faults during solenoid disconnection
4. Raise vehicle securely on jack stands at all four corners, ensuring minimum 24 inches clearance under transmission pan
5. Remove front skid plate if equipped (4WD models may have additional shielding)
6. Place large drain pan under transmission - expect 8-10 quarts of fluid during initial drain
7. Clean exterior of transmission pan and surrounding area with degreaser to prevent contamination
8. Take photos of transmission wiring harness routing and solenoid connector positions for reference during reassembly

Procedure

1. 1

   Drain transmission fluid
   Locate transmission drain plug on bottom of transmission pan. Using appropriate socket, loosen drain plug slowly and allow fluid to drain completely into drain pan. This will take 10-15 minutes. Remove drain plug completely and inspect condition of crush washer. Clean drain plug threads with wire brush and set aside with new crush washer.
   Torque spec

   Drain Plug42 Nm (31 lb-ft)
2. 2

   Remove transmission pan
   Loosen all transmission pan bolts in criss-cross pattern, starting from center and working outward. Leave two bolts at opposite corners slightly threaded. Carefully tap pan with rubber mallet to break gasket seal. Support pan while removing final two bolts as residual fluid will drain. Lower pan carefully and pour remaining fluid into drain pan. Remove and discard old gasket from pan and transmission housing mating surface.
   ⚠Expect 1-2 quarts of residual fluid to spill when pan is lowered. Position drain pan to catch additional fluid.
   Torque spec

   Pan Bolts20 Nm (15 lb-ft)
3. 3

   Remove transmission filter
   Locate transmission filter secured to valve body. Remove filter retaining bolts and carefully pull filter straight down from valve body. Inspect filter for metal debris or excessive clutch material - excessive contamination may indicate additional transmission damage requiring further diagnosis. Clean filter mounting surface on valve body with lint-free towel.
4. 4

   Disconnect solenoid electrical connectors
   Identify all solenoid electrical connectors on valve body. The 8L90 has multiple solenoids including shift solenoids, pressure control solenoids, and TCC solenoid. Carefully release connector lock tabs by pressing release mechanism while gently pulling connector straight out. Do not twist or rock connectors. Label each connector position with tape if not already photographed. Note the internal wiring harness routing through valve body passages.
   ⚠Connector release tabs are fragile plastic. Apply pressure only to designated release points to avoid breaking tabs.
5. 5

   Remove valve body retaining bolts
   Locate all valve body retaining bolts - typically 18-20 bolts of varying lengths around perimeter and through center section. Use parts organizer to track bolt positions as they are different lengths. Remove bolts in reverse criss-cross pattern starting from outer edges. Note locations of any wiring harness clips or ground straps attached to valve body bolts. Once all bolts are removed, carefully lower valve body approximately 2 inches but do not fully remove yet.
   ℹ️Valve body bolts are different lengths. Take photos or create diagram showing exact position of each bolt length for proper reassembly.
6. 6

   Separate valve body and access separator plate
   With valve body lowered, carefully tilt to access separator plate between valve body and transmission case. The separator plate contains critical check balls and orifices. Work slowly and support valve body weight. Remove separator plate retaining screws if present. Carefully lift separator plate and inspect for check balls - count and document position of all check balls. The 8L90 typically has 5-7 check balls in specific locations. Place check balls in organized tray noting exact positions.
   ⚠️Check balls must be reinstalled in exact original positions. Incorrect ball placement will cause catastrophic transmission failure. Document positions with photos before removal.
7. 7

   Remove old shift solenoids
   With valve body accessible, locate all shift solenoids. The 1-2-3-4 shift solenoid pack and 5-6-7-8 shift solenoid pack are typically secured with Torx bolts. Remove retaining bolts and carefully extract each solenoid assembly. Inspect solenoid bores for debris or scoring. Note orientation and alignment features - solenoids have specific indexing to prevent incorrect installation. Remove pressure control solenoids and TCC solenoid using same method.
   Torque spec

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

   Clean valve body and inspect passages
   With all solenoids removed, thoroughly clean valve body casting with lint-free towels and non-chlorinated brake cleaner. Inspect all fluid passages for debris or blockage. Clean solenoid bores with brake cleaner and compressed air (low pressure, 30 psi max). Examine separator plate surfaces and clean with brake cleaner. Replace separator plate gaskets with new gaskets from kit. Inspect valve body for any cracks or damage to casting.
   ⚠Use only low-pressure compressed air (maximum 30 psi) to avoid damaging internal valve body components or forcing debris deeper into passages.
9. 9

   Install new shift solenoids
   Remove new solenoids from packaging and inspect for shipping damage. Verify part numbers match transmission requirements. Lubricate solenoid O-rings lightly with clean Dexron VI ATF. Install each solenoid into correct bore, ensuring proper orientation using alignment pins or tabs. Hand-thread retaining bolts first to verify proper seating. Torque solenoid retaining bolts to specification in criss-cross pattern. Install pressure control solenoids and TCC solenoid using same procedure.
   ⚠Never install solenoids dry. Lubricate O-rings with transmission fluid to prevent seal damage during installation.
   Torque spec

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

    Reinstall separator plate and check balls
    Place new separator plate gaskets on valve body mating surface, ensuring all holes align properly. Install all check balls in documented positions - verify each ball location against photos taken during disassembly. Check balls must drop freely into their pockets. Place separator plate carefully over check balls, ensuring plate does not dislodge any balls. Verify all fluid passages align through gaskets and plate.
    ⚠️Double-check that all check balls are in correct positions before installing separator plate. This is critical and cannot be verified after assembly.
11. 11

    Reinstall valve body assembly
    Carefully raise valve body assembly into position against transmission case, ensuring separator plate and gaskets remain aligned. Start all valve body retaining bolts by hand, ensuring correct length bolt in each position per documentation. Tighten bolts in criss-cross pattern from center outward in three stages: finger-tight, then 50% torque, then final torque specification. Ensure wiring harness routes properly and is not pinched between valve body and case.
12. 12

    Reconnect solenoid electrical connectors
    Reconnect all solenoid electrical connectors to proper positions using reference photos. Each connector should click audibly when fully seated. Gently tug each connector to verify positive lock engagement. Route internal wiring harness through proper channels in valve body to prevent pinching or chafing. Verify no connectors are crossed or forced onto wrong solenoids.
13. 13

    Install new transmission filter
    Install new transmission filter to valve body, ensuring filter seal seats properly in valve body recess. Install filter retaining bolts and torque to specification if specific torque is provided by filter manufacturer, otherwise tighten firmly by hand. Verify filter is secure and does not move when lightly pulled.
14. 14

    Clean and install transmission pan
    Thoroughly clean transmission pan interior with brake cleaner and lint-free towels. Clean pan gasket mating surface with plastic scraper to remove all old gasket material - surface must be completely clean and flat. Clean transmission case gasket surface similarly. Install new pan gasket per manufacturer instructions (some use RTV sealant, others are dry gaskets). Position pan carefully to align all bolt holes. Install all pan bolts hand-tight first, then torque in criss-cross pattern from center outward.
    Torque spec

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

    Install drain plug and refill transmission
    Install new crush washer on drain plug. Thread drain plug into pan by hand, then torque to specification. Locate transmission fill plug on passenger side of transmission case. Remove fill plug. Using transmission fluid pump or funnel with long hose, add approximately 5 quarts of Dexron VI ATF through fill hole. Reinstall fill plug temporarily. Reconnect negative battery cable. Start engine and allow to idle in Park. With engine running and transmission in Park, remove fill plug and continue adding fluid slowly until fluid begins to drip from fill hole at operating temperature (160-180°F). Reinstall fill plug and torque to specification.
    ⚠Transmission must be at operating temperature (160-180°F) for accurate fluid level check. Cold fill level will be incorrect.
    Torque spec

    Drain Plug42 Nm (31 lb-ft)

    Fill Plug42 Nm (31 lb-ft)

Reassembly

1. Reinstall front skid plate if equipped, ensuring proper torque on mounting bolts
2. Lower vehicle from jack stands and verify parking brake releases properly
3. Check for fluid leaks around transmission pan, drain plug, and fill plug with engine running
4. Verify no transmission fluid drips after 5-minute idle period

Verification

• With engine at operating temperature, verify proper fluid level by removing fill plug - fluid should drip slowly from fill hole
• Test drive vehicle through all gear ranges, verifying smooth shifts from 1st through 8th gear under light acceleration
• Perform multiple upshifts and downshifts, ensuring no harsh engagement, slipping, or delayed shifts
• Check for diagnostic trouble codes using scan tool - verify no transmission-related codes are present
• Monitor transmission temperature during test drive - should remain between 180-220°F during normal operation
• Verify TCC (torque converter clutch) lockup occurs smoothly in upper gears without shudder
• Re-check fluid level after test drive and top off if necessary
• Inspect transmission pan and drain plug area for leaks after test drive - address any seepage immediately

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