GM Confirms Gen-3 10-Speed Valve Body: What Changed vs. Gen-2 (10L60/80/90) Service Bulletin # 25-NA-334

Greg Nelson
Oct 30
2 min read

Timeline

~Aug 2025: First Gen-3 service valve bodies begin appearing in the field (Mr. GregWrench- Youtube)
Oct 29, 2025: GM issues Service Bulletin # 25-NA-334, formally documenting the change for service.

Source: GM Service Bulletin # 25-NA-334 (facts summarized here)

Vehicle Coverage (from the bulletin)

Cadillac: CT4, CT5, Escalade (various MYs 2021–2024 in the bulletin’s table)

Chevrolet: Camaro; Silverado 1500 (LTD J21 VIN 5=W/Y, and New J22 VIN 5=A/D); Suburban; Tahoe

GMC: Sierra 1500 (Limited J21 VIN 5=8/9, and New J22 VIN 5=H/U); Yukon models

Engines referenced: LSY, L3B, L84, L87, LM2, LZ0, LTG, LGX, LT1, LT4

Transmissions (10-speed RPOs): MQA, MQ2, MQC, MHS, MHO, MHU, MI1, MI2, MI4, MQB

Regions: North America plus select global markets (Middle East; Mercosur countries; West South America; Philippines; Australia/New Zealand).

What Changed in Gen-3 (confirmed)

Robustness & debris tolerance: internal updates for sediment mitigation.
Auxiliary valve body eliminated; functions consolidated into the main assembly.
Relocations:
- Default Solenoid → mounted to the thick plate.
- Mode Valve & PCS → moved to the solenoid body.
- TCC Solenoid → relocated to the valve-body half on the case side.
Simplified architecture: streamlined internal valving/flow, simplified harness, solenoid cover deleted.
Park Inhibit Solenoid (ETRS; 10L80/90 only): connector may be tucked; if the application uses it and it’s left disconnected, DTC P18A3 will set. Transfer the solenoid from the old valve body where required (some apps don’t use it).
Active Warm-Up / TBV: for certain applications, the internal TBV lineup is removed; the casting port is open/blank, with the TBV located externally. RPOs called out: MQB/MQC (diesel full-size truck & SUV) and MQA/MQ2 (Cadillac car).
Fasteners updated: bolt locations change vs. Gen-2; the bolt kit P/N 24073070 (M6×68, M6×100, M6×45) is included with the Gen-3 valve body and is required if the VB is removed for other repairs.

Tech Takeaways

Expect a Gen-3 unit (with included bolt kit) when servicing covered vehicles.
Use the correct bolt lengths/pattern from SI—don’t reuse old hardware.
On ETRS apps, verify/transfer/connect the Park Inhibit Solenoid to avoid P18A3.
For specified RPOs, don’t look for an internal TBV—it’s external by design on Gen-3.
Verify connector locks after the harness simplification and solenoid relocations.
Owner Notes

The redesign targets reliability and serviceability. If you’ve noticed unusual shift behavior, ask your service advisor about Gen-3 valve body availability for your VIN/application.

Video Reference

I’ll walk through these changes with original diagrams and bench shots in the companion video: