You need to cover the inside of the main chamber with a light layer of wheel-bearing grease. This must also be applied to every surface that will take the gasket, the cylindrical section in the top, around the perimeter of the flapper, and on the brass bushings that fit between the two halves. Place a very light layer on the slider parts to make a good seal. I also added a bit around the brass cam and its pin, just for good measure.

Two of the three motors I rebuilt now work like a champ! The wipers on my car move faster than they ever did. All-in-all, I'd say that this project was quite successful.