Just unloaded a 1990 Honda. Think it is the Attack model, it has the green lighted button that must be the rear differential lock. Dash light lights when in ultra low and button is lit. Not sure this works. My worst problem is that the real time 4 wheel drive does not work. Truck will not back up a very slight gravel hill. Rear left tire digs deep hole and thats it. Anyone know how to trouble shoot these problems. When in ultra low gears I can hear sound in rear of truck that must be the rear locker. Only hear sound when in ultra low gears. Not as concerned about rear diff lock as I am the 4 wheel drive. With out 4wd this truck is useless. Thanks for any help!
Perhaps you could jack the truck up and let it idle in first gear, all 4 wheels should spin if in diff lock, i really don't know past that. I'm sure someone on this forum could suggest something. I know there is a way to disconnect the front drive shaft so that the truck can be towed, disabling the 4wd. Perhaps this was done when it was in transport, and it never got re-connected? Best of luck and keep us posted. -mark