HO DDA40X w/DCC & Sound, Undecorated

Key Features

  • Genesis driveline with two dynamically balanced five pole skew wound motors and dual flywheels on each
  • All-wheel drive and electrical pick-up
  • Factory installed dual SoundTraxx Tsunami sound and DCC decoders
  • Tsunami sounds are compatible with both DCC and DC operation
  • Authentic sounds recorded from Union Pacific DDA40X #6936
  • See-through dynamic brake intakes with grid details
  • Etched windshield wipers and see-through walkways above fuel tank
  • Etched radiator and dynamic brake fan grilles
  • Minimum 28" radius recommended


The model designation, DDA40X, comes from two “D” (four axle) trucks, “A” for a cab, “40” to indicate the use of the 16-cylinder 645E3 engine as in the GP40 and SD40, and X to indicate some experimental features. The first of the experimental features was an uprating of the 645E3 engine from 3,000-horsepower to the 645E3A engine with 3,300 horsepower. Another feature was the ability to perform a self-load test (checking that the alternator was producing power) without an external load test box to absorb the electrical power created. Next there was the usage of modular control circuits replacing considerable amounts of wiring. There was one other major difference between the Centennials and most regular freight units and that was the use of the 59:18 gear ratio that allowed 90 MPH operation instead of the standard 62:15 ratio that had a maximum of 75 miles per hour.

The DDA40X was a massive locomotive, 98 feet, 5 inches long, 17 feet four inches tall with 8,200-gallon fuel tanks and an operational weight of 545,432 pounds. They were delivered on two orders: the first order was for 25 units, numbers 6900 through 6924, delivered between April and December 1969. The second order was for 22 units, numbers 6925 through 6946, delivered between June 1970 and September 1971. Each cost $551,168.

Over the years, the Centennials underwent various modifications. The horns were originally mounted between the first and second radiator fans. Later they were moved to the cab roof. Two units were equipped with sirens as an experimental means of warning maintenance of the way personnel of the approaching train. Various types of strobe lights, flashers, and rotary beacons were installed on the DDA40Xs to make them more visible. Number 6936, still operating in UP’s Heritage Fleet, was modified with exposed bearings on the trucks, air conditioning and a new nose door following a grade crossing collision on November 30, 2000. The paint also changed. The first order was delivered with “Union Pacific Railroad” lettering in the shield. This was changed to just “Union Pacific” by painted out the “Railroad” with blue paint. After 1974, the shields just had “Union Pacific” lettering. Number 6936 got UP’s winged shield herald that adorns the nose of today’s engines, when it was repaired after the collision.

The DDA40Xs operated on almost any type of UP mainline freight trains including priority manifests, the California Livestock Special, secondary trains, and even coal and grain trains. However, their primary assignment was to hotshot Trailer on Flat Car (TOFC) or more commonly, piggyback trains, between North Platte, Nebraska and Los Angeles, Ogden, Utah, and Portland, Oregon. In the 1970s, these trains carried names and symbols like the Overland Mail, Los Angeles Expediter (LAX), Portland Expediter (SPX), Van, and Super Van. In this service, the Centennials averaged 20,000 miles a month and were over the one million mile mark in just five years.

Two DDA40Xs were destroyed in wrecks. Number 6903 was involved in a rear end collision with a Santa Fe train on Cajon Pass on April 6, 1974. Number 6921 was wrecked on August 27, 1978 at Point of Rocks, Wyoming. In 1981, the Centennials fell victim to a recession and a new policy of locomotive standardization. Regardless of their effectiveness, the Centennials were out of favor, replaced by groups of 3000 horsepower SD40-2s and C30-7s. The units went into storage. In 1982, all 45 were moved to Yermo for storage and they remained there until 1984, when 25 were overhauled and put back into service. The reactivation lasted until April 1985. Twelve DDA40Xs have been preserved. In addition, one unit, number 6936, remains in UP’s heritage fleet and sees service on special trains.


DCC: Equipped
SOUND: Equipped
ERA: 1969 - Present
Minimum Age Recommendation: 14 years
Is Assembly Required: Yes

HO DDA40X w/DCC & Sound, Undecorated



Out of Stock

This product is discontinued.