The third of the Santa Fe's "Big Three", alongside the 2900/3700-series 4-8-4s and 5011-series 2-10-4s, was the 3460-series Hudsons. In 1927, ATSF had ordered ten of the 4-6-4 wheel arrangement, but like the Berkshires that Santa Fe purchased the same year, they were a 1923 locomotive with a 1927 wheel arrangement. They were really little more than a 3400-series Pacific with a larger firebox and a 4-wheel trailing truck, down to the 73" drivers, and ATSF even seemed to recognize this in that they picked up where the 3400-series Pacifics, #3400-#3449, left off, with the first of the 4-6-4s being #3450.
In 1937, applying the lessons learned on the 3700-series 4-8-4s, Baldwin constructed an additional six 4-6-4s, #3460-#3465. The boiler package was very similar to a 3700/2900-series, rated at the 300psi of the later wartime engines. It ran on 84" drivers, meaning that mechanically it was also very comparable to the Milwaukee Road F7 4-6-4s and C&NW E-4 4-6-4s in terms of driver size and boiler pressure, as well as near-identical cylinder sizes. Shortly after deliver, in December of 1937, the #3461 led a train from Los Angeles all the way to Chicago a distance of 2,227 miles to set a world's distance record for a steam locomotive., averaging 45mph, including stops, with extended 90mph running.
Its worth noting that after only 2 months in service, Santa Fe contact Baldwin with a litany of complaints, including many steam leaks, misalignments, and overheated bearings and bushings, likely caused by the high boiler pressure finding any weak points in the design. Whether any of the other 3460s were so afflicted, and what Baldwin's response was, is lost to time. A rebuild in 1944 gave them a new arrangement of flues and tubes, a water circulator and two thermic syphons, and a Worthington feedwater heater, resulting in what was the largest and most powerful of the 4-6-4 wheel arrangement, although like the C&NW E-4s, they struggled to exceed 90mph for reasons never determined.
The 3460s were the first of the Santa Fe's "Big Three" to fall, simply because they were a one-trick pony. The 4-8-4s were primarily passenger power, but proved capable in freight service, and the 2-10-4s were primarily freight power but could pinch hit in passenger service if required. The 3460s though, with six 84" drivers, were just too slippery to work in any sort of freight service. The closest they came was when they were assigned to the Fast Mail Express, a mix of heavyweight and lightweight mail cars with the occasional coach tagged on the end. In the late 1940's Santa Fe limited the cutoff to 60% to reduce the tendency to slip the drivers at high speed on wet rail, and this made them even less suitable for any dual service use. In 1949, #3463 was assigned to Clovis on the Scout as a test run. All the way from Clovis to Belen, about 200 miles, is on a grade, 1% westbound ruling and 1.25% eastbound ruling and the 3460s were shown to be inferior to the 4-8-4s on this territory, and that confirmed that the 3460's were best suited for the territory east of Wellington, and there they stayed until retirement. Bt May, 1951, the 3460s were only averaging 362 miles per day, and by February, 1952, they were only averaging 278 miles per day. On December 3, 1953, the #3463, the last in service, was drained and stored and never was called for duty again. Meanwhile, the 2900s/3700s, and 5001/5011s stayed active right up until 1957.