So they all have the center diff lock capability, just with or without the switch?
The short answer is "Yes" in reference to Full Time LC's.
With regards to 80 series, 91 and 92 came with the switch. 93-97 did not. The wiring is present, and it's very easy to add the switch if one should choose to do so.
Regardless of year, the CDL does engage when the transfer case is put in to Low. A CDL switch merely allows the use of the CDL while in High range.
-Mike
A CDL switch merely allows the use of the CDL while in High range. Mike
It also allows you to use low range WITHOUT locking the center dif. This can be very handy too!