southern pacific o scale 4449

[trainguyoregon]

I recently purchased a new southern pacific it derails every time it goes through a gargraves switch 072. It seems that the drive wheels hit the derail part of the switch,If you remove the derail part of the switch it goes through fine, but other trains then have problems. It acts like the four small front wheels are not pulling the locomotive over enough to clear. Thanks any ideas?

[r0gruth]

Have you checked the gauge of the wheels on this loco?

[trainguyoregon]

No I have not.  Would you be able to advise me on how I would go about doing that?

Thanks for your reply