Take it apart again and remove the Chopper assembly
. Then get in there and turn the end of the motor shaft that was coupled to the chopper assembly. See if it feels smooth when you give the motor a spin or if it's rough.
If it's noisy and rough sounding when you spin it by hand you can be it will be noisy when running at higher speeds too.
In this case you would need to replace the motor-pump
. I replace a lot of these motor because of noise problems.