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This problem can be very frustrating to get undone. The purpose for the second latch is for when the cable breaks it won't let the tire fall off. Unfortunately, the latch rusts and will not operate properly.
You have to hold up the tire with another jack on both sides to take the pressure off the cable.
Let about 6" of cable out and at the bottom of the latch, you will see a sleeve. Working the sleeve up into the latch and moving the latch up and down should release it. Use lots of WD 40 to lube the latch. It is not an easy task. A lot of times we have to cut the cable and replace the hoist, if it too rusted to release.
Here is the instructions from the service manual.
The key is to get the sleeve to move up, this is what releases the latch.
Tire Hoist Secondary Latch Mechanism
Important: If the spare tire hoist has been fully raised without a spare tire in place, the secondary latch mechanism may have engaged. If this has occurred, the hoist will not lower and the following steps will need to be followed:
- Rotate the hoist shaft counterclockwise until approximately 15 cm (6 in) of cable (1) is exposed.
- While holding the latch pin (3), fully depress the latch button (2) and release the secondary latch from the hoist assembly. Some side-to-side and/or up-and-down movement may be necessary to disengage the latch mechanism.
- Continue rotating the hoist shaft counterclockwise in order to lower the hoist the rest of the way.
- If this does not release the secondary latch, the spare tire hoist will need to be replaced. See the following procedure.