09 Tacoma 4x4 2.7 5-speed 4-wheel seems tight clunks when back to 2-wheel

Please help!! Had this checked out and here is what they found: Tested the 4wd shift lock actuator. Power and ground is being sent to actuator. Tried to manually put power and ground to see if it is functioning. It did not function. Took off actuator and tested out of vehicle to see if it failed,or if the issue is in the front differential. Removed actuator from differential and bench tested. The acuator is working correctly and not binding or sticking. Plugged the actuator back in and did not reinstall to the differential and it was working correctly. When removing it some metal flakes were seen in the fluid. Made sure the syncro moved freely and it does. When moving the cyncro into the locking gear the syncro does bind and skips while trying to lock into place. 79,000 and had all bottom fluids changed at about a year ago. Dont use 4wd very much. Any insight would be greatly appreciated.