Best answer I found looks like it is from the owner's manual or technical manual... 3rd post.
www.greatlakes4x4.com
Trucks -
Four Wheel Drive And All Wheel Drive
"dinghy" Towing Is Permitted On Four Wheel Drive Trucks Only When Equipped With: - T Trucks Equipped With A New Process 231 Transfer Case (rpo Np2) - K Trucks Equipped With A New Process 241 Transfer Case(rpo Np2) - K Trucks Equipped With A Borg-warner 1370/4401/4470 Transfer Case, And The Transfer Case Is Placed In The Neutral Position. - K Trucks Equipped With A New Process 246 Transfer Case (rpo Np8)
In Order To Determine The Transfer Case Model, Locate The Identification Tag. This Tag Attaches To The Rear Case Half And Provides The Transfer Case Model Number (figures 1 And 2). Only Vehicles Equipped With New Process 231/241/246 Or Borg-warner 1370/4401/4470 Model Transfer Cases Can Be Dinghy Towed With The Transfer Case In Neutral.
Important: The Following All Wheel Drive And Four Wheel Drive Vehicles Should Not Be Dinghy Towed Unless The Propeller Shafts Are First Removed.
- K Trucks Equipped With The Optional Electric Shift Transfer Case, New Process 243 (rpo Np1) (no Neutral) - T Trucks Equipped With The Optional Electric Shift Transfer Case, New Process 233 (rpo Np1) (no Neutral) - Syclone, Typhoon, L Van And Bravada Which Are Equipped With The Borg-warner 4472 Transfer Case (no Neutral) And The Nvg136 Transfer Case - T Trucks Equipped With The New Process 207 Transfer Case (no Oil Pump) - K Trucks Equipped With The New Process 208 Transfer Case (no Oil Pump)
The Transfer Cases In These All Wheel Drive Or Four Wheel Drive Vehicles Either Have No Neutral Position Or Internal Oil Pump To Provide Lubrication While Being Towed. To Properly Tow These Vehicles, The Vehicle Should Be Placed On A Platform Trailer With All Four Tires Off The Ground. Towing With All Four Tires On The Ground Should Be Avoided. In Rare Cases When Towing With All Four Tires On The Ground Is Unavoidable, Both Front And Rear Propeller Shafts Must Be Removed In Order To Prevent Damage To The Transfer Case And/or Transmission. Follow The Applicable Service Manual Removal/installation Procedure As Front And Rear Propeller Shafts Are Matched To Attaching Components At Assembly.
TOWING PROCEDURE
THE CORRECT DINGHY TOWING PROCEDURE THAT ALL CUSTOMERS SHOULD FOLLOW IS GIVEN BELOW.
NOTICE: EXTRA CARE SHOULD BE USED WHENEVER TOWING ANOTHER VEHICLE. THE TOWING VEHICLE'S GCWR SHOULD NOT BE EXCEEDED BY ADDING THE WEIGHT OF THE DINGHY TOWED VEHICLE OR VEHICLE DAMAGE MAY RESULT.
1. FIRMLY SET THE PARKING BRAKE.
2. PLACE THE AUTOMATIC TRANSMISSION IN "P" (PARK) OR THE MANUAL TRANSMISSION IN THE LOWEST GEAR (1ST).
3. SECURELY ATTACH THE VEHICLE BEING TOWED TO THE TOW VEHICLE.
4. IF EQUIPPED, PLACE THE TRANSFER CASE SHIFT LEVER IN "N" (NEUTRAL).
CAUTION:
SHIFTING THE TRANSFER CASE TO NEUTRAL CAN CAUSE THE VEHICLE TO ROLL, EVEN IF THE TRANSMISSION IS IN PARK (AUTOMATIC) OR 1ST GEAR (MANUAL), AND MAY CAUSE PERSONAL INJURY.
5. RELEASE THE PARKING BRAKE ONLY AFTER THE VEHICLE BEING TOWED IS FIRMLY ATTACHED TO THE TOW VEHICLE.
6. INSERT THE KEY INTO THE IGNITION SWITCH AND TURN THE KEY ONE NOTCH FORWARD OF THE LOCK POSITION. THIS PLACES THE KEY INTO THE OFF POSITION, WHICH UNLOCKS THE STEERING COLUMN WHILE PREVENTING BATTERY DRAIN. UNLOCKING THE STEERING COLUMN WILL ALLOW FOR PROPER MOVEMENT OF THE FRONT WHEELS AND TIRES DURING TOWING.