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Union Pacific Steam Locomotives, 1915-1962

Part 14, UP 3600 to UP 3718

This page was last updated on December 2, 2015.

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UP 2-8-8-2 -- 3 locomotives (compound)

1915 UP
Number
First
Number
Builder Builder
Number
Date
Built
Date
Vacated
Later
Number
Notes
UP 3600 (1st) UP 2000 Baldwin 33981 Nov 1909 1917 OSL 3700 (1st) 1
UP 3601 (1st) UP 2001 Baldwin 33982 Nov 1909 1917 OSL 3701 (1st) 2
UP 3602 (1st) UP 2002 Baldwin 33983 Nov 1909 1917 OSL 3702 (1st) 3

Description:

CS Class: MC-1
Cabside Class: MC-57
Drive Wheel Diameter: 57 inches
Cylinders: 26-40x30 inches
Valve Gear:
Maximum Tractive Effort: 94,880 pounds
Weight on Drivers: 394,150 pounds
Weight in Working Order (Engine Only): 425,900 pounds
Weight in Working Order (Engine and Tender): 596,400 pounds
Fuel: Coal

General Notes:

a. Mallet Consolidation (MC)
b. UP 3600-3602 were built as UP 2000-2002 in 1909; renumbered to UP 3600-3602 in 1915.
c. UP 3600-3602 were sold to OSL in 1917; assigned as helper locomotives on Kings Hill eastbound out of Glenns Ferry, Idaho.
d. For additional information see "Ocean Toads" by James Ehernberger, in The Streamliner, Volume 5, Number 2, page13

Notes:

1. UP 3600 (1st) was built as UP 2000 in 1909; to UP 3600 (1st) in 1915; to OSL 3700 (1st) in 1917; vacated in 1928
2. UP 3601 (1st) was built as UP 2001 in 1909; to UP 3601 (1st) in 1915; to OSL 3701 (1st) in 1917; vacated in 1928
3. UP 3602 (1st) was built as UP 2002 in 1909; to UP 3602 (1st) in 1915; to OSL 3702 (1st) in 1917; vacated in 1928
   

UP 2-8-8-0 -- 15 locomotives (compound)

Road
Number
Builder Builder
Number
Date
Built
Fuel Date Converted
To Simple
UP Number
As Simple
UP 3600 (2nd) Schenectady 58262 May 1918 Coal Oct 1943 UP 3500 (2nd)
UP 3601 (2nd) Schenectady 58263 May 1918 Oil Jul 1944 UP 3501 (2nd)
UP 3602 (2nd) Schenectady 58264 May 1918 Coal Sep 1942 UP 3502 (2nd)
UP 3603 Schenectady 58265 May 1918 Coal Oct 1943 UP 3503 (2nd)
UP 3604 Schenectady 58266 May 1918 Oil Sep 1944 UP 3504 (2nd)
UP 3605 Schenectady 58267 May 1918 Coal May 1943 UP 3505 (2nd)
UP 3606 Schenectady 58268 May 1918 Oil Nov 1944 UP 3506 (2nd)
UP 3607 Schenectady 58269 May 1918 Coal Sep 1943 UP 3507 (2nd)
UP 3608 Schenectady 58270 May 1918 Oil Dec 1944 UP 3508 (2nd)
UP 3609 Schenectady 58271 May 1918 Coal Jul 1942 UP 3509 (2nd)
UP 3610 Schenectady 58272 May 1918 Coal Jul 1942 UP 3510 (2nd)
UP 3611 Schenectady 58273 May 1918 Coal Nov 1943 UP 3511 (2nd)
UP 3612 Schenectady 58274 May 1918 Coal Sep 1942 UP 3512 (2nd)
UP 3613 Schenectady 58275 May 1918 Oil Aug 1944 UP 3513 (2nd)
UP 3614 Schenectady 58276 May 1918 Coal Jan 1943 UP 3514 (2nd)

Description:

CS Class: MC-2
Cabside Class: MC-57
Drive Wheel Diameter: 57 inches (rebuilt to 59 inches in 1942-1944)
Cylinders: 26&41x32 inches (rebuilt to 23&23x30 inches in 1942-1944)
Maximum Tractive Effort: 103,000 pounds
Weight on Drivers: 457,500 pounds
Weight in Working Order (Engine Only): 487,500 pounds
Weight in Working Order (Engine and Tender): 704,700 pounds
Fuel: Coal

General Notes:

a. Mallet Compound (MC)
b. Built as compound locomotives in 1918; rebuilt to simple locomotives in 1942-1944 (including changing drivers from 57 inches to 59 inches) and renumbered to UP 3500 series
c. UP 3600-3614 built as coal burners; five locomotives (UP 3601-3604, 3606, 3608, 3613) converted to oil burners after 1932 and before 1938
d. Oil burners converted back to coal burners in November 1947 through January 1948; assigned to coal branches in the Rock Springs, Wyoming area
.  

UP 2-8-8-0 -- 19 locomotives (compound)

Road
Number
Builder Builder
Number
Date
Built
Fuel Date Converted
To Simple
UP Number
As Simple
UP 3615 Brooks 61905 Jul 1920 Coal Aug 1943 UP 3515
UP 3616 Brooks 61906 Jul 1920 Coal Aug 1942 UP 3516
UP 3617 Brooks 61907 Jul 1920 Coal Jun 1937 UP 3517
UP 3618 Brooks 61908 Jul 1920 Coal Sep 1937 UP 3518
UP 3619 Brooks 61909 Jul 1920 Coal May 1942 UP 3519
UP 3620 Brooks 61910 Aug 1920 Oil Jul 1937 UP 3520
UP 3621 Brooks 61911 Aug 1920 Oil Feb 1939 UP 3521
UP 3622 Brooks 61912 Aug 1920 Oil Nov 1937 UP 3522
UP 3623 Brooks 61913 Aug 1920 Oil Sep 1937 UP 3523
UP 3624 Brooks 61914 Aug 1920 Oil Aug 1937 UP 3524
UP 3625 Brooks 61915 Aug 1920 Oil Apr 1937 UP 3525
UP 3626 Brooks 61916 Aug 1920 Oil Mar 1938 UP 3526
UP 3627 Brooks 61917 Aug 1920 Oil Jun 1937 UP 3527
UP 3628 Brooks 61918 Aug 1920 Oil Nov 1937 UP 3528
UP 3629 Brooks 61919 Aug 1920 Oil May 1937 UP 3529
UP 3630 Brooks 61920 Aug 1920 Oil Aug 1937 UP 3530
UP 3631 Brooks 61921 Aug 1920 Oil Jun 1937 UP 3531
UP 3632 Brooks 61922 Aug 1920 Oil Jun 1937 UP 3532
UP 3633 Brooks 61923 Sep 1920 Coal Sep 1937 UP 3533

Description:

CS Class: MC-3
Cabside Class: MC-57
Drive Wheel Diameter: 57 inches (rebuilt to 59 inches in 1937-1943)
Cylinders: 26&41x32 inches (rebuilt to 23&23x30 inches in 1937-1943)
Maximum Tractive Effort: 106,900 pounds
Weight on Drivers: 472,000 pounds
Weight in Working Order (Engine Only): 502,500 pounds
Weight in Working Order (Engine and Tender): 720,600 pounds
Fuel: (see above)

General Notes:

a. Mallet Compound (MC)
b. Built as compound locomotives in 1920; rebuilt to simple locomotives in 1937-1943 (including changing drivers from 57 inches to 59 inches) and renumbered to UP 3500 series
c. UP 3620-3632 (13 locomotives) were converted from coal burners to oil burners before 1938
d. UP 3620-3629 were leased to OWRR&N in 1920.
e. UP 3630-3633 were leased to OSL in 1920.
   

UP 2-8-8-0 -- 5 locomotives (compound)

Road
Number
Builder Builder
Number
Date
Built
Fuel Date Converted
To Simple
UP Number
As Simple
UP 3634 Brooks 63771 Mar 1923 Coal Aug 1943 UP 3534
UP 3635 Brooks 63772 Mar 1923 Coal Jan 1942 UP 3535
UP 3636 Brooks 63773 Mar 1923 Oil Jun 1937 UP 3536
UP 3637 Brooks 63774 Mar 1923 Oil Nov 1937 UP 3537
UP 3638 Brooks 63775 Mar 1923 Oil May 1937 UP 3538

Description:

CS Class: MC-4
Cabside Class: MC-57
Drive Wheel Diameter: 57 inches (rebuilt to 59 inches in 1937-1943)
Cylinders: 26&41x32 inches (rebuilt to 23&23x30 inches in 1937-1943)
Maximum Tractive Effort: 106,900 pounds
Weight on Drivers: 472,000 pounds
Weight in Working Order (Engine Only): 502,500 pounds
Weight in Working Order (Engine and Tender): 720,600 pounds
Fuel: (see above)

General Notes:

a. Mallet Compound (MC)
b. Built as compound locomotives in 1923; rebuilt to simple locomotives in 1937-1943 (including changing drivers from 57 inches to 59 inches) and renumbered to UP 3500 series
c. UP 3636-3638 were converted from coal burners to oil burners before 1938, the date of the updated folio diagram book.
d. UP 3637 was equipped with a tender traction booster removed from an OWRR&N 9700 class 4-12-2
   

UP 2-8-8-0 -- 5 locomotives (compound)

Road
Number
Builder Builder
Number
Date
Built
Fuel Date Converted
To Simple
UP Number
As Simple
UP 3639 Brooks 64402 Aug 1923 Coal Jan 1938 UP 3539
UP 3640 Brooks 64403 Aug 1923 Coal Sep 1942 UP 3540
UP 3641 Brooks 64404 Aug 1923 Coal Mar 1942 UP 3541
UP 3642 Brooks 64405 Aug 1923 Oil Aug 1937 UP 3542
UP 3643 Brooks 64406 Aug 1923 Coal Aug 1943 UP 3543

Description:

CS Class: MC-5
Cabside Class: MC-57
Drive Wheel Diameter: 57 inches (rebuilt to 59 inches in 1937-1943)
Cylinders: 26&41x32 inches (rebuilt to 23&23x30 inches in 1937-1943)
Maximum Tractive Effort: 106,900 pounds
Weight on Drivers: 472,000 pounds
Weight in Working Order (Engine Only): 502,500 pounds
Weight in Working Order (Engine and Tender): 720,600 pounds
Fuel: (see above)

General Notes:

a. Mallet Compound (MC)
b. Built as compound locomotives in 1923; rebuilt to simple locomotives in 1937-1943 (including changing drivers from 57 inches to 59 inches) and renumbered to UP 3500 series
c. UP 3642 was converted from a coal burner to a oil burner before 1938
d. UP 3642 was equipped with a tender traction booster removed from an OWRR&N 9700 class 4-12-2
   

UP 2-8-8-0 -- 1 locomotive (compound)

1923 UP
Number
First
Number
Date To
UP
Builder Builder
Number
Date
Built
Date Converted
To Simple
UP Number
As Simple
UP 3644 OSL 3703 (1st) Oct 1923 Schenectady 58277 May 1918 Apr 1942 UP 3544

Description:

CS Class: MC-2
Cabside Class: MC-57
Drive Wheel Diameter: 57 inches (rebuilt to 59 inches in 1942)
Cylinders: 26&41x32 inches (rebuilt to 23&23x30 inches in 1942)
Maximum Tractive Effort: 103,000 pounds
Weight on Drivers: 457,500 pounds
Weight in Working Order (Engine Only): 487,500 pounds
Weight in Working Order (Engine and Tender): 704,700 pounds
Fuel: Coal

General Notes:

a. Mallet Compound (MC)
b. UP 3644 was built as OSL 3703 as a compound locomotive; to UP 3644 in 1923; converted to simple in 1942 and renumbered to UP 3544
c. Built as coal burner (as OSL 3703, as UP 3644, and as UP 3544); converted to oil burner in 1943-1945; converted to coal burner in November 1947 to January 1948 and assigned to Rock Springs coal runs.
   

UP 2-8-8-0 -- 20 locomotives (compound)

1915
Number
Builder Builder
Number
Date
Built
Fuel Date Converted
To Simple
UP Number
As Simple
UP 3645 Brooks 65665 Jun 1924 Coal May 1937 UP 3545
UP 3646 Brooks 65666 Jun 1924 Coal Dec 1943 UP 3546
UP 3647 Brooks 65667 Jun 1924 Coal Jun 1937 UP 3547
UP 3648 Brooks 65668 Jun 1924 Oil Aug 1937 UP 3548
UP 3649 Brooks 65669 Jun 1924 Oil May 1937 UP 3549
UP 3650 Brooks 65670 Jul 1924 Coal Apr 1937 UP 3550
UP 3651 Brooks 65671 Jul 1924 Oil Jul 1937 UP 3551
UP 3652 Brooks 65672 Jul 1924 Oil Oct 1937 UP 3552
UP 3653 Brooks 65673 Jul 1924 Oil Oct 1937 UP 3553
UP 3654 Brooks 65674 Jul 1924 Oil Aug 1937 UP 3554
UP 3655 Brooks 65675 Jul 1924 Coal Jun 1937 UP 3555
UP 3656 Brooks 65676 Jul 1924 Coal Feb 1942 UP 3556
UP 3657 Brooks 65677 Jul 1924 Coal Jun 1937 UP 3557
UP 3658 Brooks 65678 Jul 1924 Coal Jun 1937 UP 3558
UP 3659 Brooks 65679 Jul 1924 Coal Dec 1943 UP 3559
UP 3660 Brooks 65680 Jul 1924 Coal Oct 1937 UP 3560
UP 3661 Brooks 65681 Jul 1924 Oil Jun 1938 UP 3561
UP 3662 Brooks 65682 Jul 1924 Coal May 1937 UP 3562
UP 3663 Brooks 65683 Jul 1924 Coal Jul 1943 UP 3563
UP 3664 Brooks 65684 Jul 1924 Oil Aug 1937 UP 3564

Description:

CS Class: MC-6
Cabside Class: MC-57
Drive Wheel Diameter: 57 inches (rebuilt to 59 inches in 1937-1943)
Cylinders: 26&41x32 inches (rebuilt to 23&23x30 inches in 1937-1943)
Maximum Tractive Effort: 106,900 pounds
Weight on Drivers: 472,000 pounds
Weight in Working Order (Engine Only): 502,500 pounds
Weight in Working Order (Engine and Tender): 720,600 pounds
Fuel: (see above)

General Notes:

a. Mallet Compound (MC)
b. Built as compound locomotives in 1924; rebuilt to simple locomotives in 1937-1943 (including changing drivers from 57 inches to 59 inches) and renumbered to UP 3500 series
c. Eight locomotives (UP 3648, 3649, 3651-3654, 3661, 3664) were converted to oil burners before 1938
d. Seven locomotives (UP 3648, 3649, 3651-3654, 3664) were equipped with a tender traction booster removed from an OWRR&N 9700 class 4-12-2s
   

UP 2-8-8-2 -- 5 locomotives (ex N&W Y-3) (USRA pattern)

1945 UP
Number
Previous
Number
Date To
UP
Builder Builder
Number
Date
Built
Date
Vacated
UP 3670 N&W 2030 Jun 1945 Schenectady 61098 May 1919 Nov 1947
UP 3671 N&W 2020 Jun 1945 Schenectady 61088 Apr 1919 Nov 1947
UP 3672 N&W 2025 Jun 1945 Schenectady 61093 May 1919 Jul 1947
UP 3673 N&W 2041 Jun 1945 Schenectady 61109 May 1919 Dec 1947
UP 3674 N&W 2013 Jun 1945 Schenectady 61081 Apr 1919 Nov 1947

Description:

Cabside Class: 2-8-8-2
Drive Wheel Diameter: 57 inches
Cylinders: 25&39x32 inches
Maximum Tractive Effort: 114,154 pounds
Weight on Drivers: 485,200 pounds
Weight in Working Order (Engine Only): 539,000 pounds
Weight in Working Order (Engine and Tender): 825,533 pounds
Fuel: Coal

General Notes:

a. Mallet Compound (MC)
b. These five locomotives were built as N&W Y-3; to UP in 1945 to help move wartime traffic across Wyoming; vacated and scrapped 1947 as soon as traffic slowed down.
   

OSL 2-8-8-2 -- 3 locomotives (compound)

1917 OSL
Number
First
Number
Second
Number
Date To
OSL
Builder Builder
Number
Date
Built
Date
Vacated
OSL 3700 UP 2000 UP 3600 (1st) 1917 Baldwin 33981 Nov 1909 Nov 1928
OSL 3701 UP 2001 UP 3601 (1st) 1917 Baldwin 33982 Nov 1909 Nov 1928
OSL 3702 UP 2002 UP 3602 (1st) 1917 Baldwin 33983 Nov 1909 Nov 1928

Description:

CS Class: MC-1
Cabside Class: MC-57
Drive Wheel Diameter: 57 inches
Cylinders: 26&40x30 inches
Weight on Drivers: 394,150 pounds
Weight in Working Order (Engine Only): 425,900 pounds
Weight in Working Order (Engine and Tender): 596,400 pounds
Maximum Tractive Effort: 94,880 pounds
Fuel: Coal

General Notes:

a. Mallet Compound (MC)
b. Built as UP 2000-2002 in 1909; renumbered to UP 3600-3602 in 1915-1916; sold to OSL in 1917 and renumbered OSL 3700-3702.
c. Assigned to Glenns Ferry, Idaho, for eastbound helper service on Kings Hill.
d. Retired in 1928 with completion of second main track on Kings Hill grade.
e. See "Ocean Toads, 1909 Monster Mallets", by James L Ehernberger, The Streamliner, Volume 5, Number 2, pages 13-24
   

OSL 2-8-8-0 -- 1 locomotive (compound)

Road
Number
Builder Builder
Number
Date
Built
Date
Vacated
1923 UP
Number
OSL 3703 (1st) Schenectady 58277 May 1918 Oct 1923 UP 3644

Description:

CS Class: MC-2
Cabside Class: MC-57
Drive Wheel Diameter: 57 inches (rebuilt to 59 inches in 1942)
Cylinders: 26&41x32 inches (rebuilt to 23&23x30 inches in 1942)
Maximum Tractive Effort: 103,000 pounds
Weight on Drivers: 457,500 pounds
Weight in Working Order (Engine Only): 487,500 pounds
Weight in Working Order (Engine and Tender): 704,700 pounds
Fuel: Coal

General Notes:

a. Mallet Compound (MC)
b. Built as OSL 3703 in 1918; to UP 3644 in 1923; converted from compound to simple in 1942 and renumbered to UP 3544
c. Built as coal burner (as OSL 3703, as UP 3644, and as UP 3544); converted to oil burner in 1943-1945; converted to coal burner in November 1947 to January 1948 and assigned to Rock Springs coal runs.
d. OSL 3703 was equipped with a Street stoker.
   

OSL 2-8-8-0 -- 2 locomotives (compound)

Road
Number
Builder Builder
Number
Date
Built
Fuel Date Converted
To Simple
OSL Number
As Simple
OSL 3704 (1st) Brooks 63779 Mar 1923 Coal Apr 1944 OSL 3565
OSL 3705 (1st) Brooks 63780 Mar 1923 Oil Apr 1944 OSL 3566

Description:

CS Class: MC-4
Cabside Class: MC-57
Drive Wheel Diameter: 57 inches (rebuilt to 59 inches in 1944)
Cylinders: 26&41x32 inches (rebuilt to 23&23x30 inches in 1944)
Maximum Tractive Effort: 106,900 pounds
Weight on Drivers: 472,000 pounds
Weight in Working Order (Engine Only): 502,500 pounds
Weight in Working Order (Engine and Tender): 720,600 pounds
Fuel: (see above)

General Notes:

a. Mallet Compound (MC)
b. OSL 3705 was converted from a coal burner to an oil burner between 1930 and 1938.
   

UP 4-6-6-4 -- 8 locomotives "Light Challengers"

1949 UP
Number
First
Number
Second
Number
Date To
3700 Series
Builder Builder
Number
Date
Built
Date
Vacated
1950 UP
Number
UP 3701 (2nd) UP 3901 UP 3801 (2nd) 1949 Schenectady 68746 Sep 1936 1950 UP 3801 (2nd)
UP 3702 (2nd) UP 3902 UP 3802 (2nd) 1949 Schenectady 68747 Sep 1936 1950 UP 3802 (2nd)
(UP 3703)                
UP 3704 (2nd) UP 3904 UP 3804 (2nd) 1949 Schenectady 68749 Sep 1936 1950 UP 3804 (2nd)
(UP 3705)                
(UP 3706)                
UP 3707 (1st) UP 3907 UP 3807 1949 Schenectady 68752 Sep 1936 1950 UP 3807
(UP 3708)                
UP 3709 (1st) UP 3909 UP 3809 1949 Schenectady 68754 Sep 1936 1950 UP 3809
UP 3710 (1st) UP 3910 UP 3810 1949 Schenectady 68755 Sep 1936 1950 UP 3810
UP 3711 (1st) UP 3911 UP 3811 1949 Schenectady 68756 Sep 1936 1950 UP 3811
(UP 3712)                
(UP 3713)                
UP 3714 (1st) UP 3914 UP 3814 1949 Schenectady 68759 Sep 1936 1950 UP 3814

Description:

CS Class: CSA-1
Cabside Class: CSA-69
Drive Wheel Diameter: 69 inches
Cylinders: 22&22x32 inches
Maximum Tractive Effort: 97,400 pounds
Weight on Drivers: 386,000 pounds (as built) (in later years their weight-on-drivers varied between 399,660 pounds and 407,610 pounds depending on type of feedwater heater and weight of front engine)
Weight in Working Order (Engine Only): 566,000 pounds (as built) (in later years their weight varied between 569,820 pounds and 590,550 pounds depending on type of feedwater heater and weight of front engine)
Weight in Working Order (Engine and Tender): 876,000 pounds (as built) (varied between 892,420 pounds and 915,000 pounds depending on type of feedwater heater and weight of front engine))
Fuel: Coal (converted from oil in 1949; converted back to oil in 1950)

General Notes:

a. Challenger Simple Articulated (CSA)
b. UP 3701-3714 were built as UP 3901-3914 in 1936; to UP 3801-3814 in 1944; to UP 3701-3714 (coal burners) in 1949; back to UP 3801-3814 (oil burners) in 1950
c. Eight locomotives (UP 3801, 3802, 3804, 3807, 3809, 3810, 3811, 3814) were converted to coal burners in 1949 and renumbered to UP 3701-3714; all eight locomotives were converted back to oil burners in 1950 and renumbered back to their 3800 series numbers
d. (Read a brief narrative written by Allen Copeland in 1978)
   

UP 4-6-6-4 -- 8 locomotives

1952 UP
Number
First
Number
Date To
3700 Series
Builder Builder
Number
Date
Built
Date
Vacated
UP 3700 (2nd) UP 3930 (2nd) 1952 Schenectady 72792 Aug 1944 Jan 1961
UP 3701 (3rd) UP 3931 (2nd) 1952 Schenectady 72793 Aug 1944 Jan 1961
UP 3702 (3rd) UP 3932 (2nd) 1952 Schenectady 72794 Aug 1944 Mar 1961
UP 3703 (2nd) UP 3934 (2nd) 1952 Schenectady 72796 Aug 1944 Mar 1961
UP 3704 (3rd) UP 3937 (2nd) 1952 Schenectady 72799 Aug 1944 Dec 1958
UP 3705 (2nd) UP 3938 (2nd) 1952 Schenectady 72800 Aug 1944 Oct 1959
UP 3706 UP 3943 1952 Schenectady 72805 Aug 1944 Mar 1961
UP 3707 (2nd) UP 3944 1952 Schenectady 72806 Aug 1944 Jun 1961

Description:

Cabside Class: 4664-5
Drive Wheel Diameter: 69 inches
Cylinders: 21&21x32 inches
Maximum Tractive Effort: 97,350 pounds
Weight on Drivers: 406,200 pounds
Weight in Working Order (Engine Only): 634,500 pounds
Weight in Working Order (Engine and Tender): 1,071,000 pounds
Fuel: Oil (converted from coal in 1952)

General Notes:

a. These eight UP 3900 series locomotives were converted from coal to oil in 1952 and renumbered to UP 3700-3707
   

UP 4-6-6-4 -- 10 locomotives

1952 UP
Number
First
Number
Builder Builder
Number
Date
Built
Date
Vacated
Notes
UP 3708 UP 3975 Schenectady 70158 Jun 1943 Mar 1961  
UP 3709 (2nd) UP 3976 Schenectady 70159 Jun 1943 Oct 1959  
UP 3710 (2nd) UP 3977 Schenectady 70160 Jun 1943 Nov 1961 1
UP 3711 (2nd) UP 3978 Schenectady 70161 Jun 1943 Dec 1958  
UP 3712 UP 3979 Schenectady 70162 Jun 1943 Mar 1961  
UP 3713 UP 3980 Schenectady 70169 Jun 1943 Jun 1961  
UP 3714 (2nd) UP 3981 Schenectady 70170 Jun 1943 Dec 1958  
UP 3715 UP 3982 Schenectady 70171 Jun 1943 Jul 1962  
UP 3716 UP 3983 Schenectady 70172 Jun 1943 Oct 1959  
UP 3717 (2nd) UP 3984 Schenectady 70173 Jun 1943 Oct 1959  

Description:

Cabside Class: 4664-5
Drive Wheel Diameter: 69 inches
Cylinders: 21&21x32 inches
Maximum Tractive Effort: 97,350 pounds
Weight on Drivers: 406,200 pounds
Weight in Working Order (Engine Only): 634,500 pounds
Weight in Working Order (Engine and Tender): 1,071,000 pounds
Fuel: Oil (converted from coal-burners in 1945)

General Notes:

a. UP 3708-3717 were built as UP 3975-3984 in 1943; converted from coal burners to oil burners in 1945 and assigned to service on the Northwestern District (OWRR&N); renumbered to UP 3700 series in 1952

Notes:

1. UP 3710 (2nd) was used in snow melting service at North Platte, Nebraska; renumbered to UP 900079 "Roadway Locomotive" in November 1961; retired in May 1968 and donated to City of North Platte, Nebraska; displayed as UP 3977 in Cody Park.
   

UP 4-6-6-4 -- 2 locomotives "Light Challengers"

1949-1950
UP Number
First
Number
Second
Number
Date To
3700 Series
Builder Builder
Number
Date
Built
Date
Vacated
Later
Number
UP 3717 (1st) UP 3917 UP 3817 1949 Schenectady 68926 Aug 1937 1950 UP 3817
UP 3718 UP 3918 UP 3818 1949 Schenectady 68927 Aug 1937 1950 UP 3818

Description:

CS Class: CSA-2
Cabside Class: CSA-69
Drive Wheel Diameter: 69 inches
Cylinders: 22&22x32 inches
Maximum Tractive Effort: 97,400 pounds
Weight on Drivers: 403,000 pounds (as built) (in later years their weight-on-drivers varied between 399,660 pounds and 407,610 pounds depending on type of feedwater heater and weight of front engine)
Weight in Working Order (Engine Only): 582,000 pounds (as built) (in later years their weight varied between 569,820 pounds and 590,550 pounds depending on type of feedwater heater and weight of front engine)
Weight in Working Order (Engine and Tender, UP 3815-3833): 894,000 pounds (as built) (varied between 892,420 pounds and 915,000 pounds depending on type of feedwater heater and weight of front engine)
Fuel: Coal (converted from oil in 1949; converted back to oil in 1950)

General Notes:

a. UP 3717 and 3718 were built as UP 3917 and 3918 in 1937; to UP 3817 and 3818 in were built as oil-burners; converted to coal-burners in 1949 and renumbered to UP 3717 and 3718; converted back to oil burners in 1950 and renumbered back to UP 3817 and 3818.
b. (Read a brief narrative written by Allen Copeland in 1978)

###