Lube the worm bearings and the gear case ,I actually use castrol 10 w 40 high mileage just a few drops with a toothpick .Had it ready to do a oil change .Cleaned all the gunk out of the metal gear cases,make sure the wiring to the trucks is solid connection.Lube the MOTOR BEARINGS, universals joints on the drive shaft the same way ,then clean up the excess with a cue tip ,a few if you like me.C lean the wheels with some alcohol.If all else fails and it has a stock decoder , Get another! These are not noiseless decoders and put out a lot of noise witch is not good at all.These are very good heavy engines that need good lube and electronic controll.I put sound in mine and have the best of both worlds .A Spectrum Diesel with full function sound that will creep tie to tie or pull a 25 car coal train by it self.
Pat
Pat