Endgate and Front Side Door Lock Cylinder Coding

The endgate and front side door lock cylinder uses 8 of the 10 key cut positions, 3-10 when counting from the key head. The tumbler orientations alternate in adjacent locations from side with 4 each side.

Fig 1: View of front side door lock cylinder tumblers

Courtesy of GENERAL MOTORS CORP.

1. Hold the uncoded rotor (1) positioned so the side of the rotational stop lug is facing downward, as shown.
2. Insert one tumbler spring (2) each into the 4 holes from the upper side.
3. The first tumbler to be loaded will be key cut position number 3, the third number in the key code. Determine the cut depth at this position and install the corresponding tumbler (3) into the tumbler slot nearest the front of the rotor-CP.
4. In the same manner, determine the cut depth and corresponding tumbler and install the 3 remaining tumblers (3) into the tumbler slots located at key cut positions 5, 7, and 9.
5. Check for correct loading by holding the tumblers (3) in position and fully inserting the matching key into the rotor. All tumblers should be flush with the outside diameter of the rotor.
6. Rotate the rotor (1) so that the side with the rotational stop lug is facing upward and then remove the matching key. Remember the tumblers (3) are not self-retaining and must be held in place.
7. Insert one tumbler spring (2) each into the 4 tumbler spring holes.
8. The first tumbler to be loaded will be key cut position number 4. Determine the cut depth at this position and install the corresponding tumbler (3) into the tumbler slot nearest the front of the rotor-CP.
9. In the same manner, determine the cut depth and corresponding tumbler and install the 3 remaining tumblers (3) into the tumbler slots located at key cut positions 6, 8, and 10.
10. Check for correct loading by holding the tumblers (3) in position and fully inserting the matching key into the rotor (1). All tumblers should be flush with the outside diameter of the rotor.
11. Lightly lubricate tumbler (3) and rotor (1) surfaces using the lubrication provided.
12. With the matching key fully inserted into coded rotor, install the coded rotor into the rotor case (4) fully. Make sure rotor is stopped at approximately 60 degrees when you rotate to clockwise and counterclockwise with the key, approximately 120 degrees total.
13. Remove the key, the rotor stays in the rotor case, and install the lock cylinder cap (5) on the rotor case (4). Crimp the side edge of the lock cylinder cap (5) around the rotor case depressions, 2 places.
14. For endgate cylinders, proceed to step 16. For door lock cylinders, hold the cylinder assembly so the key opening is facing down, 6 o'clock, and the cylinder cut out is facing you, so tumblers are visible. Slide the return spring (6) around the rotor top, 12 o'clock position. The return spring (6) resides between the rotor and rotor case.
15. Keep the cylinder assembly in the same orientation, key opening at 6 o'clock and rotor top at 12 o'clock. The return spring consists of a lower and upper spring tab. Locate the lower spring to the left side of the cylinder tab. This cylinder tab is located at the 12 o'clock position and resembles a hook shape. No force is required against spring tension. Then, working against spring tension, rotate the upper spring tab to the right side of the cylinder tab. The upper spring tab will finally reside in the hook shape of the cylinder tab.
16. Keep the cylinder assembly in the same orientation, key opening at 6 o'clock and rotor top at 12 o'clock. Orient lever (7) with tab at facing down at 6 o'clock. Lower the lever (7) onto the rotor top so the tab fits between spring tab upper and spring tab lower.
17. Install the retaining ring (8) in the groove at the end of the rotor (1) to secure the lever (7) to the cylinder. Concave surface of retaining ring (8) should touch the lever.
18. Install the clip (9) as shown.