Taking one step back here.
The 80 came in many different configurations when it comes to 4wd, depending on market and choice of options.
Some did not have permanent 4wd and had mechanical selection of either 2H, 4H or 4L. A transfer box like that has no differential: There is no CDL switch, and no possibility for one either. When in 4wd, the front and rear are always locked to eachother, meaning that 4wd is for off-tarmac use only. This is what it sounds like you have, Jim.
Vehicles with that type of transfer came with either only LSD in the rear, RDL, or both RDL and FDL.
Then you have all the versions with a central differential and an electric actuator for locking it, which is what has been discussed here.