2020 Chevrolet Silverado structure problems

“GM Corporate Legal has formally denied a repair for a known design flaw (TSB 18-NA-383) that has caused progressive structural corrosion and water intrusion underneath the cab carpets near vehicle electrical routing since 2024. The certified GM technician explicitly identified GM Technical Service Bulletin #18-NA-383 as the governing bulletin for this exact issue. The technician’s diagnostic notes state word-for-word: "...i inspected the truck and the rear window is leaking i can see water stains on the window and the head liner has a big water stain. the floor is not rotted out but the rear of the rockers and the cab corners are rotting and bubbling under the paint." This proves the structural rot is being caused from the inside out by a factory defect, not environmental road salt. I have a duplicate large packet that I sent including +15 dated photos to GM corporate/legal back in August.”

“The contact owns a 2020 Chevrolet Silverado 1500. The contact stated that while vehicle was parked, water was leaking inside the rear interior of the cab. The dealer was notified of the failure, and the vehicle was serviced but the failure persisted. The manufacturer was notified of the failure. The failure mileage was approximately 38,000.”

“Component/System That Failed: The rear sliding window assembly leaked water into the cabin due to a manufacturing defect in the urethane seal and third brake light area. The window has been replaced and no longer leaks, but the water caused lasting damage to the headliner with trapped moisture. Components are available for inspection. Safety/Health Risk: The leak saturated the headliner, creating a serious risk of mold growth. My pregnant wife and unborn baby could be exposed to mold spores. Water intrusion also risks slippery floors, fogging, and potential electrical issues. Dealer Confirmation: Folsom Chevrolet confirmed the leak, replaced the window, and recommended full headliner replacement due to staining and mold risk. This is covered in GM TSB 18-NA-383. Manufacturer Awareness: GM has known about this defect for years but denied full repair (Claim #9582-9999). Symptoms: No warning lights. Leak first noticed in September 2025 after rains began. Due to dry California summer, it went unnoticed earlier, even though the defect likely started while the vehicle was still within the 3-year warranty period (mileage was over 36k when noticed). Additional Info:…”

“Rear window is leaking onto the carpet beneath it creating mold and could allow water to enter the SRS module. Currently i have a tray blocking that water but without that the SRS system could be affected by the water entering the cabin through the rear window.”

“The Rear Window leaks when it rains on the truck. I brought it back to the GM Chevy dealer and they applied a sealant. it immediately leaked right after. the truck now smells musty and im assuming there is mold growth. it has been at the dealership for the past two weeks while they try to figure it out”

“The contact owns a 2020 Chevrolet Silverado 1500. The contact stated while the vehicle was parked inside the garage, he noticed a crack on the frame and there was water running back into the interior of the cabin and the backrest of the seat. There were no warning lights illuminated. On a separate occasion, the contact experienced water entering the cabin while it was raining due to the frame cracks. The contact contacted the water doctors and provided a diagnosis of frame crack in multiple locations, allowing water to enter the cabin of the vehicle and underneath the spoiler. The local dealer was contacted; however, the vehicle was not repaired because it was not under recall. The manufacturer was made aware of the failure. The failure mileage was approximately 40,000.”