99 silverado z71 stuck in 4wd

I have A 99 silverado and it is stuck in 4wd when I hit the 2wd switch it blinks and I can hear clicking then goes back to 4wd and also when I hit the button I can hear the t case shift motor trying to switch over but just goes back to 4wd does anyone have any ideas or advice on what it could be I would appreciate it thank you

Most common cause is the encoder motor.

OK thank you I will swap it out tomorrow

Instead of just replacing it, remove it from the side of the case and see if it will move. Then see it the shaft on the case will move, and how easily it turns. The vehicle may have to be in neutral with the wheels free to rotate to shift the case, as in elevated on jack stands or a lift. Align the shaft to the motor before assembly.

since it does try to move did you check the T case fluid level and condition ? these do leak because of a manufacturing defect very common rub inside the T case then it leaks .

fluid needs replacing @40K miles .
then if that is good the codes should be pulled GM drive train capable scanner then this will reveal what is the issue most times.

to replace the encoder as was mentioned lifting the wheels off ground to install is some times required. encoders come in the neutral position so the fork in T case may require to be rotated to align ..

the encoder will not rotate because it is always locked unless the lock has power to it then it releases ..