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

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Model Train Help EBook

Southern Pacific
Class Mt-3

18 units built

built by SP
4328 4329
4330 4331 4332 4333 4334 4335 4336 4337 4338 4339
4340 4341 4342 4343 4344 4345

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. 4330 and 4342 were the only Mt-3's with Boxpok discs.

These were built with sport cabs, apparently the first such application to home-built engines. The first five engines were built with cast-steel engine beds, the first such application on the Southern Pacific (see The 4300 4-8-2's by Church).

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 4326, 4330, 4342, 4351, 4354 and 4365 were fitted with Boxpok discs. The installation of multiple bearing crossheads and disc wheels was not always simultaneous, some engines did not get both, and some got neither (4337 and 4341). Only occasionally were disc drivers and multiple bearing crossheads added when the skyline case was installed (4332). 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
4328no ? no ? 6-29-48 EP
4329no 3-2-46 Sac 11-6-39 Sac
43301-23-52 LA by 1953 3-7-47 Og
4331by 1951 no 5-20-41 Sac
43327-29-49 Sac 7-29-49 Sac 7-29-49 Sac
433311-16-49 Ogden no 2-27-41 EP
43343-17-52 Ogden 3-17-52 Ogden 12-26-40 LA
43351-13-47 EP 1-13-47 EP 11-20-40 Sac
4336after 1950 (6-10-52 LA?) no 4-28-41 Sac
4337no no 5-31-41 EP
43383-21-50 Sac 8-13-47 Sac 6-7-41 LA
4339no 6-14-50 LA 10-21-40 EP
434011-12-52 EP no 10-16-48 EP
4341no no 10-20-39 Sac
43427-25-49 LA 7-25-49 LA 8-7-41 Sac
434311-30-49 LA no 5-9-41 LA
43444-19-47 LA 4-19-47 LA 1-18-40 Sac
43456-14-47 Sac 6-14-47 Sac 11-27-40 Sac


  • 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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