GP-40 diesel locomotive item no. 63552 not running properly

[ACDC]

I purchased a GP-40 diesel locomotive, Bachmann item no 63552 from a reputable eBay vendor.  The packaging had never been opened.  Yet, when I ran the loco, it sputtered and ran erratically both forward and reverse. There was clearly intermittent electrical pick up. The motor/gears are very loud. There is no manufacturing date on the product but, although it looks identical to the loco that came with my Thunder Valley set I purchased one year ago, it is heavier and appears to be more substantial. I surmise it may be NOS and may have sat around unsold and unused.  I cleaned the wheels and trucks with isopropyl alcohol. After removing the shell, there is no apparent oil or grease stains anywhere. The motor spins freely by hand friction or if 12 volts DC are applied to the chassis or wheels.  There is no strange noise.  It is a split chassis design and I have not disassembled the chassis.  Any advice would be welcome.......Thanks and Happy Holidays !

[Yard Master]

Hi ACDC,

Following up on your thread about the Thunder Valley, your 63552 is the pre-redesign version of our N scale GP40, so it probably was unused new old stock. You can contact our service department for more troubleshooting.

[ACDC]

Thank you Yard Master.  Turns out that this loco is not covered under warranty because I purchased it on ebay from a non-authorized vendor.  If instead of sending it in for service, I disassemble it and clean the running gear.  What parts require grease as opposed to oil?

[Yard Master]

Hi ACDC,

We recommend to use a small amount of light gear oil (such as E-Z Lube item no. 99984) on the motor and wheel bearings, as well as conductive contact lube (E-Z Lube item no. 99981) for electrical pickups/contacts. You can use a small amount of grease on the worm gears, but use a light application to avoid jamming them.