Thumping Noise when 4x4 disengage

[Pinas_guy]

Hi to all,

I’m hearing some thumping noise when I tried to turn while the RED light still flashing on the center of the 4x4 indicator after pushing the 4x4 button (turn OFF 4x4). Usually, it will take some time for the RED light to come OFF after disengaging or pushing the 4x4 button, between 3 to 10 seconds, and when you tried to turn left or right while the RED is flashing but NONE of the four wheel indicated, you hear the thumping. So immediately I stop the turn and get the truck to drive straight. This would stop the thumping noise. Also I would need to lift my foot a few times from the gas and some time that would do the trick to turn the RED flashing indicator. I’m thinking the center differential are not totally disengage yet, but why would it make a noise? Is the system vacuumed actuated? Maybe I an air leak on the diaphragm actuator and building up vacuum to fully disengage.

Thanks

[GoldenR]

Normal operation on Toyota Sequoia, you should be driving straight and not in a turn while engages or disengaging 4x4 system. Its better to be on snow, gravel, dirt road when engaging the system. The system is not vacuum controlled, electrical motor actuated, one on the transaxle (center) and one for the forward differential. The noise you are hearing is from the forward differential actuator engaging or disengaging the linkage.