jh504 said:
....... It does have the locker..........
Don't confuse the Center Differential Lock with Axle Differential Lockers.
All 80 series have the Center Differential lock. Front and rear differential locks did not come around until 93. 91-92 will have a Center diff lock switch on the dash standard to allow you to lock the center diff in 4HI. The CDL switch was optional 93+. The CDL will (should) engage automatically when the shifter is placed in 4LO 91-97.
For F/R diff locks, you want to look for a switch like the one immediately to the left of the steering column:
If you are looking at a 93-97 80 series that has the F/R lockers, test them out like this:
Go to a gravel or dirt area.
Engage 4Lo
ABS and CDL lights should illuminate. If they don't, go forward or backward a little.
After the CDL is engaged, turn the locker switch to RR and wait for the Rear Locker light to come on. If it doesn't drive in a circle or figure 8.
Once the RR locker engages, turn the switch to the F locker position and do the same if it doesn't engage.