GP40 noise

[mjb]

Hey guys/gals... Was gifted a GP40...its very noisy... gear / whine type of noise. I'm not a train guy. It only gets set up once a year around the Christmas tree for the kids. Not sure how old it is but its newer than the old pancake style motors. I've completely disassembled both trucks expecting to find a bad gear somewhere, but everything looks good, nothing obvious. It was a little dirty but not bad at all. Any tips or suggestions ??
Thanks in advance for any input.   Mark