2006 locking rear end

[Darrelllee]

I am new here and looking for advice if anyone can help me.
I own a 2006 silverado Z71 with the locking differential and it seems to be locked in posi .
I plan to remove the cover to inspect but this type of rear end is new to me
what should I be looking for and what could have caused the differential to lock up?
Any suggestions

 

[Off Road King]

a sized up LSD, before you take off the cover, jack up the rear end and spin the passanger side rear wheel, if the driver's side truns then you know for sure it's locked, spin it both ways and see if the other one truns, it shouldnt trun if it's un locked because the driver's side has the posi trac wheel

 

[Darrelllee]

Thank you for the info

 

[Darrelllee]

Here is what was wrong
I pulled the cover to inspect for possible damage or broken parts and the unit is good no breakage or damage but I did find evidence of clutch pack residue on the assembly , the unit was due for service and I suspect that due to the residue on the assembly that is what caused the locker to engauge and not let go .
The night that it locked up it was extremly cold out and the truck rarely is left outside it is always in a heated garage. I washed the unit down and applied new fliud to the assembly before reinstalling the cover I then filled the unit with new fluid and rotated the wheels to ensure everything was completely bathed in lubricant and took it out on dry pavement and everything works as it should.