Locking the differential ?

[ARPCAxPREZ@aol.com]

I'm a little confused on the application of locking the
differential..............I have a ' 87 5KsQ and on the dash there is a 2
postion differential switch.  Turning the switch to the first position locks
the front differential, and turning to the second position locks the rear
differential..............Does this mean...............if I run the rear of
the car off the road -- we'll say the rear end slid out onto a snowy shoulder
slope as we were rounding a turn -- Now...... do I lock the differential to
the front ? ......so the front wheels take all the power to pull the car out
?   Is this the purpose of the locking differential ?   Also when locking the
differential.......does it have to be a slippery roadway or could it be dry ?
 and  do you need to keep your speed down  or  could you drive at a normal
speed ?    Thanks for the advice
Sincerely,
Bradley Blumfeldt
Pittsburgh PA
' 87 5KsQ  plate: X X X X