I know our Armada's have open diffs that means they dont lock. My question is do they lock in 4LO? Does it split power 50/50 between front and real axels?

In 4wd Lo and Hi the torque is mechanically (solid engagement) split 50/50 F to R. The front drive shaft is tied mechanically to the rear drive shaft; there cannot be any speed difference. Active Brake Limited-Slip Differential (ABLS) uses the brakes to slow down the spinning wheel so the power transfers to the other side; that is side-to-side, not front to rear.