Transfer case / Transmission not working?

2006 TOYOTA TUNDRA
150,000 MILES • 4.7L • V8 • 4WD • AUTOMATIC
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MHUPP
I engaged 4 hi on my truck listed above while driving, all went fine. I stopped and shifted into neutral and pressed the 4 lo button. It flashed for a bit and then went solid, but when I shifted into drive it flashed again and the buzzer sounded, and a thunk sound came from below the vehicle. I shifted back into neutral and attempted to disengage 4 lo, but it did not work. I shifted into park, and there was a short grinding sound from the transmission. When the car is started, the 4 lo button flashes as well as the indicator on the dashboard. 4wd is still engaged, I spun the rear driveshaft by hand and the front one moved as well. When shifted into drive, there is no response. None of the gears work, both drive and reverse are just neutral. The car rolls freely while in drive and reverse.
Jun 8, 2025 at 9:19 AM
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STRAILER
  • ASE Certified Mechanic
  • 54,503 POSTS
  • ASE Certified Mechanic
Does the truck roll freely in park as well? If so something inside the transfer case broke. This is why the truck grinds when going into park. Here is what I think broke in the images below. Also, it could be the actuator is not fully engaging the shift fork. I would remove it with the wires connected to see if the actuator moves. Check out the images (below). Please upload pictures or videos in your response.

Jun 8, 2025 at 1:44 PM
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