NHTSA Complaint #11648413 — 2020 GMC SIERRA 1500

-Transmission valve body Failure, Wheel lock up, ABS Event, Loud Bang and a Flashing "D" on Driver Information Center (DIC) when Lightly or Moderately Accelerating Forcing an 8-7 or 8-6 Downshift -When all four tires lock up at a high rate of speed, this puts the driver, the passengers, and all others on the road at risk for injury or death. -Yes, the problem has been found in a document by my local dealer that this issue was added to my exact vehicle's service manual on 11/27/24. The document describes in detail the exact scenario I have been involved in multiple times. It is deemed as #21-NA-275. It locks up the tires randomly to the vehicle in mid acceleration at any speed including 80 miles per hour in one instance for me. -Yes, the dealership inspected it and found the issue to correlate with the newly added section to the service manual, 13333166. This document ID is 5925530 and the added information to the dealership is #21-NA-275. The GMC manufacturer has been contacted as of 3PM MST 3/14/25. Insurance doesn't deal with mechanical problems. The police will only be involved when there is death or injury. -No. The only warning that happens is simultaneously as the vehicle locks up the tires causing the driver (me) to inevitably try to save myself and others, swerving and trying to focus on not hurting myself or others but I did notice the "D" flash on one of these occasions. This is the most dangerous issue with a vehicle I have ever even considered. At any time, for any reason, all four tires can lock up at any rate of speed and cause multiple casualties. The way to fix this is to spend $3,000 which I am sure many people like myself do not have. This means there are thousands of these exact make and models of vehicles on the road right now. Please do not take this lightly as I have almost crashed multiple times with people in my vehicle due to no fault of my own.