Question about Automatic Differential Disconnect (ADD) pre 2001

What happened to your dad's truck?

 

I know this is an old post but wanted to add that: manual hubs give you the ability to lock them prior to actually needed them as well. i.e.: you are setting out and think it might snow later or going off road thru some muck and rocks. Lock the hubs beforehand and when it starts to get dicey, just pull the xfer case lever and click it into 4H or 4L: Instant "Shift-on-the-fly-4WD": no need to get out of the truck. I would routinely do this especially when I knew I was going to run into snow eventually. Only minor drawback is the tires and front axle-shafts are spinning, but not driving...until you select 4WD via the xfer case. Maybe a little more wear and tear, some extra driveline noise and reduced fuel economy... but for how long really? IMO: They were absolutely bullet-proof with only periodic grease checks required as far as maintenance. They were also all-analog with the exception of a couple of status indicator lamps on the instrument cluster.