So I replaced the lumbar support in the mega cab today and made a bit of a modification to it in the process. The part number for the adjuster is: 5166079AA and cost me 51 & change. Here's what I did.
Removed the headrest & the two shafts they fit down into. They just pull out once the headrest is removed.
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Remove the adjustment wheel by just pulling out. If you try to "unscrew" it out you may break the teeth on the wheel.
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Remove the cup behind the wheel. Two phillips head screws hold it in place.
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Then the inner cup, held in with two screws as well comes out. You can wait till you pull the cover off but I did it here:
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There's a plastic "clip" channel at the bottom rear of the seat that has to be un clipped. It was a pain in the @$$ and by far the most difficult part of the whole job. Once you get it apart just start peeling the seat cover up & out of the way. Its best to just remove it all the way.
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Rear view of the broken adjuster.
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Once the cover is off, remove the padding from the frame of the chair. Lift up at the top to get around the head rest tubes, and the side to clear the adjuster.
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Use a pair of channel locks to twist each end out of the socket. Each end has "ears" that go in the right slot.
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Once installed it looks like this when there is no tension or support.
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When the adjuster is turned for more support it tightens up and looks like this. Basically pushing the foam forward.
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More below.
Removed the headrest & the two shafts they fit down into. They just pull out once the headrest is removed.

Remove the adjustment wheel by just pulling out. If you try to "unscrew" it out you may break the teeth on the wheel.

Remove the cup behind the wheel. Two phillips head screws hold it in place.

Then the inner cup, held in with two screws as well comes out. You can wait till you pull the cover off but I did it here:

There's a plastic "clip" channel at the bottom rear of the seat that has to be un clipped. It was a pain in the @$$ and by far the most difficult part of the whole job. Once you get it apart just start peeling the seat cover up & out of the way. Its best to just remove it all the way.

Rear view of the broken adjuster.

Once the cover is off, remove the padding from the frame of the chair. Lift up at the top to get around the head rest tubes, and the side to clear the adjuster.

Use a pair of channel locks to twist each end out of the socket. Each end has "ears" that go in the right slot.

Once installed it looks like this when there is no tension or support.

When the adjuster is turned for more support it tightens up and looks like this. Basically pushing the foam forward.

More below.