Take the replacement blower motor out of its packaging and set it on a padded surface. Examine the motor for damage or manufacturer defects.
Check to ensure that the blower wheel is centered in its housing before inserting the motor shaft into the blower wheel hub. Install the mounting screws to hold the motor in place; the size and number of screws varies by Rheem furnace model. Fit the retaining nut onto the motor shaft and tighten it using an adjustable wrench.
Attach the ground wire from the motor to the blower housing. Plug the motor wiring into the wiring harness on the blower assembly. Consult the wiring diagram that came with the replacement motor for guidance, if necessary.
Hold the blower access panel to the front of the furnace cabinet. Slide the panel straight down to engage the cabinet retaining clips.
Restore the electricity to your Rheem furnace. Turn on the power from your home's main electrical service panel or flip the dedicated "On/Off" switch if your model has one. Open the gas-supply valve if you have a Rheem gas furnace.