HO GEN 4-8-8-4 Big Boy Locomotive Primed For Grime UP #4003 (ATHG-2196)

This HO-scale Athearn Genesis 4-8-8-4 Big Boy steam locomotive in Union Pacific livery, Primed for Grime UP 4003, is designed to represent an in-service Big Boy with a weathered look on a model railroad.

It features illuminated number boards and headlights, a tender back‑up light, and detailed cab and boiler details, along with synchronized chuff, whistle, bell, and other sounds from a SoundTraxx Tsunami2 system. The model runs on both DC and DCC with an on-board decoder and dual speakers for rich sound, and it offers NMRA-compatible functions with current pickup on all wheels and a minimum recommended radius of 22 inches. Road-number specific for UP #4003 includes a Primed For Grime finish to depict an in-service look, coal burner, and cooling pipes, making it an ideal starting point for adding grime and rust to match a layout’s era.