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I have an older HO scale blue box Athn. gp38-2. It runs smooth and quiet except when it hits a curve. I have medium to large radius curves, anyway when it goes into a curve it makes a grinding/vibrating sound. The tighter the curve the louder it gets. It is well lubed,wheels are straight and where they should be, gears are good and tight. I have no idea why it makes this noise. None of my other locos do this and I have several other Athn. gp38-2's. Any idea what the problem may be ? Thanks
Check the gear box for any broken gears or broken axles in the truck. Have you actually checked the wheels with an NMRA gauge? They can be prefectly straight but slightly our of gauge, cause the kind of nosie you describe.
See if the trucks swivel freely by hand. If they don't, pop the shell off and look for what's making it bind up. Are there any wires that could be rubbing against anything?
If it is an old enough BB engine, I always found the shaft between the worm gear and motor would vibrate because it was a very loose fit. I always replaced mine with a piece of metal tube cut to length. I don't remember the diameter of the tube, but it fit snugly enough that no glue was needed.
Also check to see if the motor/flywheel assembly is straight in the body. The deflection of the trucks going around a curve may be enough to cause the motor to flex just enough to cause the flywheels to rub against the body.
