Whirlpool upper rack spray arm issue

[whirlpoolio]

I suspect the upper spray arm (between the racks) is not turning. It's not being impeded by dishes, and the spray arm itself is clean inside. Dishes in the upper rack are not coming out as clean as usual.
Model number is WDF760SADB3.

Trying to figure out how to disassemble the flat tube from the bottom of the tub to the spray arm. Any idea on how to do that, and if it turns out that the tube is not clogged, what to look at next? Any help would be much appreciated!

 

[michaelz08]

It may be that your main circulation pump is on its last legs. It would result in a lack of water pressure, which could be an explanation. Or there's a bushing- I think- made of nylon between the arm and the mount that could be bad? But I'm not sure if this is an orderable part. In the parts diagram linked below, it's not listed separately.

https://s3.amazonaws.com/sm-backend-production-attachments/parts-list-W11025869-RevA.pdf