Union Pacific Railroad

General Notes:

1. UP S1 to S6 were built by UP at Omaha from retired UP GP9Bs.
2. UP S1, S2, and S3 were originally equipped to operate only with SD7 slug control units. S4, S5, and S6 were originally equipped to operate only with SD24 slug control units; all were later modified to operate with either SD7, SD24, and later, SD40 slug control units; these combinations were called ten motor slug sets.
3. Prior to being rebuilt to Slug S5, GP9B 314B was out of service for 239 days, since July 1974, because of an electrical fire.
4. UP S4 and S5 were equipped with external sand boxes in October 1980, similar to those applied to the DDA40X, DDA35, and DD35 B-unit road freight locomotives.
5. Car body of UP S6 was cut down to 77 inches in May 1985 at Salt Lake City, to improve visibility from the attached power unit.
6. The six GP9 yard slugs were originally equipped to operate only with SD7 or SD24 slug control units; all six slugs were later modified to operate with SD40 slug control units. (List of yard slugs and their paired control units)

Notes:

1. UP S1 was out of service June 1986; sold to Aaron Ferer and Sons, Omaha, Nebraska, in November 1987.
2. UP S2 was out of service May 1985; sold for scrap to Southwest Railroad Car Parts, Longview, Texas, 2 April 1987.
3. UP S3 was scrapped by UP at Omaha in September 1982.
4. UP S4 was sold for scrap to Pielet Brothers Scrap Iron & Metal, McCook, Illinois, 17 January 1990.
5. UP S5 was out of service April 1986; sold for scrap to Pielet Brothers Scrap Iron & Metal, McCook, Illinois, 17 January 1990.
6. UP S6 was sold for scrap to Pielet Brothers Scrap Iron & Metal, McCook, Illinois, 17 January 1990.

General Notes:

1. UP S7 and S8 built by UP at Omaha from retired UP SD24Bs.
2. UP S7 and S8 were originally equipped to operate only with SD24 slug control units; both slugs were later modified to operate with SD40 slug control units; these combinations were called twelve motor slug sets. (List of yard slugs and their paired control units)

Notes:

1. UP S7 was sold for scrap to Pielet Brothers Scrap Iron & Metal, McCook, Illinois, 17 January 1990.
2. UP S8 was wrecked during late April 1985 at North Platte, Nebraska; out of service May 1985; sold for scrap to Aaron Ferer and Sons, Omaha, Nebraska, in November 1987.

General Notes:

1. Rebuilt from retired MP SW7s, SW8s, and SW9s by MP Pike Avenue Shops, North Little Rock, Arkansas; mated with MP15s and, beginning in October 1990, GP38-2s.
2. UP Yard Slugs S9 to S13 had operating weight of 246,000 pounds; UP S14 to S31 had operating weight of 261,000 pounds.
3. An excellent source of information about MP's yard slugs was published by the Missouri Pacific Historical Society in "The Eagle", Volume 15, Number 4, Winter 1990, including how to build a model of one of the units.
4. UP S16-S18 (as MP 1407-1409) were first painted UP yellow and gray, with Missouri Pacific lettering, in May and July 1985 while assigned to Houston; relettered to UP S16-S18 in August and October 1988.
5. Renumbered to UPY 903-925.
6. Individual unit histories:

Notes:

1. UP S9, as MP yard slug 1206, was completed as MP's first yard slug in November 1978 and was initially mated with MP SW1200 1275; MP 1206 was renumbered to MP 1400 on 30 December 1978.
2. UP S13, S20, and S26 were converted in December 2001 and January 2002 for service as CCRCL control units for remote control switcher/slug power sets; completed as UPY 100-102.
3. UP S24 and S25 were retired in December 2000; reinstated on 11 January 2001, but as of February 2008, the units remain stored at Pine Bluff, Arkansas. (information from Kermit Geary, via email to LocoNotes discussion group, February 13, 2008)

General Notes:

1. Original total of four units; three units went to UP at merger; SP retired 1011 prior to the merger.
2. SP 1010-1013 were rebuilt by General Electric, Minneapolis, from four former L&N switchers (three NW2s and an SW7); all were initially assigned to Roseville, California, with MP15ACs.
3. Assigned UP S1-S3 in September 1997, not renumbered; assigned UPY 900-902 in December 1999, not renumbered.