installing rear wiper arm on 91 GW

[Tbeach]

Need help installing rear wiper arm. See attached pics. Purchased new rear wiper arm from TGW. There are no threads on the inside of the hole in the arm. What am I missing? Is the rear wiper motor not OEM?

Thanks for your help.

[babywag]

Flip the cover up on the rear wiper arm.
Install new arm on shaft.
Install retaining nut on shaft, and tighten VERY carefully.
Flip the cover down on the rear wiper arm.

[acct21]

Carefully dribble some PB Blaster on that big mounting but in the first pic. Do that monthly forever -- so if/when the day comes you have to remove the motor, it won't snap the threaded portion off the motor case.

[Tbeach]

thanks for the input. Will work on it this weekend.