Product review (5 stars): I hope this helps others that encounter this trouble (The top rack fail) & Amazon Site's failure to confim part compatibility!
Hello Amazon!

Your site says "Sorry we can't verify this part fits your

But, Sears (Whoa--how every low tech.) says otherwise:

From the Sears Parts Direct Web Site--

http://www.searspartsdirect.com/kitchenaid-dishwasher-parts/W10712394/0022/665/model-KUDE40FXSS4/0593/0130000.html

Part Information

This manufacturer-approved dishrack adjuster kit (part number W10712394) is for dishwashers.

Dishrack adjuster kit W10712394 includes both of the adjusters that position the upper dishrack height. Dishrack adjuster kit contains multiple parts; refer to your parts diagram for a complete list of parts included.

Follow the installation instructions included with the kit.
This Dishwasher Rack Adjuster Kit part #W10712394 is guaranteed to fit your KITCHENAID UNDERCOUNTER DISHWASHER #KUDE40FXSS4

I feel inclined to order this part from Sears but it is $41 and I am cheap.

Anyway the part  (#W10712394 ) fit the Kitchen Aid KUDE40FXSS4 and that's the truth-Ruth.