<<<Any time the pump is running there is an annoying whistleing sound.>>>
During the WASH cycle---not the DRAIN MODE---correct?
All LDF6920 dishwashers have a flawed CHOPPER (also known as Macerator).
The CHOPPER has tips on it that are too much like an indian arrowhead tip---which causes noise during the Wash cycle.
A replacement CHOPPER corrects this.
Part Number---> 5832DD4001B
To replace the Chopper:
Remove both racks
Lift/remove the Lower Wash Arm (snaps out)
Remove the *Water Tower/Tube* that runs/routes from the Filter Housing---up the back of the dishwasher---and to the top of the dishwasher.
This done by removing the Phillips screw on the Filter Housing---which has a small stainless steel tab on it.
Then unsnap the mounting tabs (with your fingers or flat screwdriver) of the Water Tube at both---the top/center of the dishwasher and the back/center of the dishwasher.
Pull the Water Tower towards the front slightly---and twist/turn to the right---until it comes out of the Filter Housing.
Use a drill to remove all of the Filter Assy screws
Lift off the Filter Assy
At the rear of the Sump Assy---there will be a round/white Valve---pull it off (re-install the black o-ring if it has come off).
Remove the IMPELLER screw (reverse-thread) and pull.
Remove the Impeller Housing (lift off)
Remove the original CHOPPER and install the new one.
Re-assemble in reverse order (verify that the black gasket is correctly seated before carefully installing the Filter Housing).