There are 3 rears..
1. open rear. one wheel spins. If you jack the rear of the truck up with both wheels off the ground and spin a wheel the other wheel will spin the opposite way. Thats an open rear.
2. A limited slip rear is a posi rear. The manufacturers call them different things I guess cause of patent rights. GM calls it a posi. Others call it limited slip. Jack the truck up with both wheels off ground and spin a wheel forward. The other wheel will spin the same direction. ( There are some LSD/posi that dont..It depends on what you got in there ,clutched or geared based. There are many variations...
3. Locker rear.. When one wheel loses traction a pin comes out and locks the other wheel. This is mechanical. whether automatic, or on command
4. There are spool rears but they are for racing/off road only..
With that said rebuild your limited slip/posi if thats what you have or install an on command locker..
Unless your a good driver a mechanical locker in the winter of slippery surface can cause you to spin out. Like when raining and going around a corner if the right tire slips the left will lock up. That will spin you right round....
Check your RPO codes for what rear you have.. Or let the guy tell you when he opens it. Or jack it up and let us know what happens when you spin a wheel. what way does the other go?
On the lockers you will hear a ratcheting...click click click...( ( We know you dont have that thought)
