[Dan Pierce]

What kinds of sounds? Grinding (Not good) Whirring?

I have run 10 different 'cow'engines and one was very noisy. I loosened the screws on the bottom and hooked up power and tightened the screws while running at a moderate speed at my work bench.

Noise lessened, but it is still my noisiest engine.

 

[Dan Pierce]

If the shaft wobbles, then it is possible it is bent or out of quarter.

When testing an engine, you need to make sure the frony and rear axles are 90 degrees apart for the side rods to work properly without jammiing and damaging the gears.

Many G scale engines have internal gears to bring motor power to the wheels, but the side rods must be aligned properly or the gears will bind/strip.