Unscrew the four screws at the base of the power rod box with a Phillips-head screwdriver. Tap the power rod box lightly with a rubber mallet to ease it off of the Bowflex structure.
Remove the plastic plug at the bottom of the defective power rod. Unscrew the Phillips-head screw and pull the power rod out of the power rod box.
Guide the replacement power rod back into the power rod box. Ensure that the slot on the bottom of the power rod matches up with the ridges at the bottom of the hole.
Secure the power rod by tightening the Phillips-head screw into the bottom. New power rods come with their own screws, whether they are replacement power rods or the upgrade package that allows for more weight.
Replace the power rod box and tighten the four Phillips-head screws. To secure the power rod box, give it a few taps with a rubber mallet.