Could be something in the food chopper #6 in this diagram
or the main motor
Sometimes if it's the main motor you can see a little trail of water reside at the bottom of were the motor connects to the sump housing
I always check the food chopper first just because it's easier when the dishwasher is installed, but being it's in his garage I would lay it on it's back and take a look at the motor to see if there is any sign of water residue like a white trail round the bottom edge of the motor.
I have replaced a lot of noisy motors in these types of dishwashers.