I've been having a 4WD issue for the past year, 4WD switch lights aren't even on, Service 4WD message stopped showing after a while. I finally managed to change out the transfer case encoder motor today, and now my 06 silverado will not even go into drive/reverse. The switch lights still aren't on and I can hear a clicking noise from the new motor whenever putting it into reverse, neutral, drive, and it makes a grinding noise if you try to put it back into park. So, now I turn off the truck before putting it into park. The way I installed was taking out the front driveshaft, taking out the old encoder motor, and gear orientation from the transfer case was different from the new encoder motor so using pliers I change the gear into proper orientation, so the new motor would fit, plugged everything back together, and now I can't even drive. Any ideas?