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That is a general CYA statement. They are referring to the main axle shaft nut. It is a 12 point nut and they are staked to the key way cut out in the axle shaft. Click on the link below for the torque info if you feel like you want to torque it.
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The only way to get the picture of the axle nut is to give you the instructions and picture of the axle shaft removal. Obviously you don't do anything with the axle shaft or hub, it was just a nice illustration of the axle nut itself that is what the manual is referring to. If you truly wanted to re torque it you need to un stake the nut and loosen it with a breaker bar then re torque it. There is one on each side. Frankly they never come loosen and you should never have to worry about it. Theoretically they could become loose as the bearings wear. The nut is accessable bu removing the hub cap if you have alloy wheels the wheel will need removed.
I hope this clears things up.
If you need anything else regarding this let me know.
If you attempt to take the nut all the way off and do not get it unstaked cleanly it can mess the nut up and possibly the threads on the shaft. If this happens replace the nut. If you get the nut unstaked cleanly and just break it loose to re tighten to check the torque I would re use the nut and just restake it.