Pinion Nut has nothing to do with the rear arms...
To check the pinion nut you remove the driveshaft and if the rear end flange wobbles around then you have an issue, but it isn't as easy as retorquing. When the pinon nut is torqued to spec it crushes a crush sleeve, if you torque it to far you will have issues and the sleeve will need to be replaced, then the rear has to come apart.
You want to make sure you use loctite on the bolts and antiseize as well on the bolts where they will sit inside the sleeves. I have the TQ specs at home but you also want to TQ them into place and make sure the arms still articulates smooth.
Perfect time to re-enforce the TQ boxes while it is all apart. I make a kit if your interested.... PM me.