California's Railroad to the U.S. 1861 - 1996

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Model Train Help EBook

Southern Pacific
Class Mt-4

21 units built

built by SP
4346 4347 4348 4349
4350 4351 4352 4353 4354 4355 4356 4357 4358 4359
4360 4361 4362 4363 4364 4365 4366

Text to follow...

From Arnold Menke: Diebert & Strapac state correctly that many 4-8-2¹s got disc drivers, but most were Universal, not Boxpok. The name Boxpok was a General Steel Castings (Commonwealth) trademark. Universal discs were made by Locomotive Finished Material Co. and had much larger, and fewer holes than GSC's Boxpok¹s. 4351, 4354, and 4365 were the only Mt-4's with Boxpok discs.

Mt-4's that were built with cast-steel engine beds had the cylinders and front bumper cast integrally, a first on the SP (see Church, The 4300 4-8-2's).
The following received Daylight paint schemes in 1946-1947: 4350, 4352, 4353, 4361, 4363. At this time an airhorn was mounted on the front of the skyline case, left side, apparently the first 4-8-2's to have them. By 1949 and into the 1950's other 4-8-2's with skyline cases received airhorns, but perhaps not all of them.

4344 and 4348 both lost their skyline casings temporarily after accidents in the 1940's. Photos of these two after removal of the case show that the steam dome and sand box were very close together on engines with skyline casings. 4344 received its second skyline case at Ogden 3-8-49. Prior to that it ran with a plain boiler for a time. 4348 was in wreck in Oregon 5-7-43. It operated without a skyline case until 3-31-49 when a new one was applied at Sacramento. Other engines had their skyline case "renewed": 4341 on 2-8-50 Ogden and 4371 on 9-24-51 Ogden.

Many Mt¹s eventually received multiple bearing crossheads. Mt-2's, of course, were built with them. Disc main drivers were applied to many of the 4300's; these were mostly Universal discs, but 4351, 4354 and 4365 were fitted with Boxpok discs. 4354's Boxpok set lasted only a few months, being replaced with a Universal pair. The installation of multiple bearing crossheads and disc wheels was not always simultaneous, some engines did not get both, and some got neither (4356). Only occasionally were disc drivers and multiple bearing crossheads added when the skyline case was installed (4364). I have listed below known dates for application of this equipment taken from SP's Descriptive Record of Locomotive cards in CSRM. Application of disc main drivers and multiple bearing crossheads sometimes was not recorded on Descriptive Record of Locomotive cards. For these engines photographic evidence must be used. Whenever I have lacked such evidence I have given "no" with a question mark to indicate that verification is needed. First entry after the engine number is the date of application of multiple bearing crossheads. Second entry is date of application of disc main drivers. Except as indicated above, Universal discs were used.

MBXH Disc main driverSkyline
43461-6-49 LA 1-6-49 LA 9-29-39 Sac
4347after 1948, by 1953no 11-31-41 Sac
43484-10-47 El Paso 3-31-49 Sac 12-21-40 Sac
434911-20-48 El Paso no 11-19-48 EP
43503-3-47 Sac no 6-28-40 Sac
4351no 12-8-47 El Paso 12-8-47 EP
43522-28-47 LA 2-28-47 LA 12-3-40 EP
4353no by 3-1947 7-23-41 LA
43542-7-49 El Paso 2-7-49 El Paso (Boxpok)
Universal by 6-1951
3-31-41 Sac
4355no ? 3-24-46 LA 11-20-40 EP
4356no no 8-30-40 LA
435711-23-49 Bakersfieldno 7-25-40 Sac
4358by 3-1954 6-12-48 Sac 6-10-40 LA
4359no ? no ? 8-25-48 EP
43601-28-50 LA 1-28-50 LA 9-30-40 EP
4361no ? no ? 5-10-40 EP
4362no 4-27-48 LA 4-21-41 EP
43633-18-47 Sac 4-29-49 Sac 1-11-41 Sac
43644-7-49 LA 4-7-49 LA 4-7-49 Note: skyline case applied at LA, not Sac as per D&S
4365no 6-28-46 Sac 10-14-39 Sac
436611-10-49 Bayshore 1-14-46 Bayshore 1-14-46 Bayshore


  • A Century of SP Steam Locomotives - Guy L. Dunscomb
  • SP Co. Steam Locomotive Compendium by Diebert & Strapac
  • The 4300 4-8-2's Southern Pacific's Mt- Class Locomotives (Revised Edition) - by Robert J. Church
  • Southern Pacific Steam Pictorial Vol.2 by Dunscomb, Dunscomb & Pecotich
  • Volume 8 -- Southern Pacific Mountain 4-8-2 Pictorial - by Duane Karam Jr. & Jeff Ainsworth, Monte Vista Publishing

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