Viscous coupling hub ?

[brea]

I removed my viscous fan coupling today and I noticed that the hub has four indentations on the hub plus the groove on the face that engages with the mounting bolt.

What is the purpose of the indentations as you can see in this picture?

 

[Stevehose]

Isn't there a piece that fits over that and the clutch from the other side?

 

[brea]

Isn't there a piece that fits over that and the clutch from the other side?

Steve, I don't think there is anything else that fits over that other than the fan coupling. Here are a few more pictures. Even the diagram shows the indentations. I was wondering if these indentations were to maybe hold bearing grease.

 

[Stevehose]

Yeah I thought piece 8 was counter-knotched but I guess not. I dont think it's for grease.

 

[HB Chris]

They serve no known purpose, don't put grease there

 

[bavbob]

My theory, they allow snug fit for the fan as if it were pressed on but easy removal. Almost like how a ball joint seats itself.

 

[brea]

Thank you for all the input!