All Time UP Diesel Roster, S Series Road Slugs

Road Slug Model S4-B — 1 unit
B-B trucks; 249,000 pounds operating weight

Road Number	First Number	Rebuild Date	Rebuilt From	Date To S50	New Number	Date To New Number
UP S50	MKT 501	Jul 1982	MKT GP40 222	20 Mar 1989	S300	1 Feb 1991

General Notes:

a.	Built as MKT road slug 501 from wrecked MKT GP40 222; renumbered and repainted to UP S50 on 20 March 1989, at the same time as matching GP40 slug control units, UP 595 and 596 (ex MKT 226, 227).
b.	Operated with UP 3000 and 3001, former MKT GP40s.

Road Slug Model S4-B — 1 unit
B-B trucks; 249,000 pounds operating weight

Road Number	First Number	Second Number	Rebuild Date	Rebuilt From	Date To S50	Date To S300	Date To UPY 926
UP S300	MKT 501	UP S50	Jul 1982	MKT GP40 222	20 Mar 1989	1 Feb 1991	17 Dec 2003

General Notes:

a.	Built as MKT road slug 501 from wrecked MKT GP40 222; renumbered and repainted to UP S50 on 20 March 1989, at the same time as matching GP40 slug control units, UP 595 and 596 (ex MKT 226, 227).
b.	Operated with UP 3000 and 3001, former MKT GP40s.
c.	Model was changed from SL-1 to S4-B on 14 April 1992; changed from freight service to switching service on same date.
d.	Renumbered to UPY 926.

Road Slug Model S5-2B — 3 units
B-B trucks; 256,000 pounds operating weight

General Notes:

a.	Rebuilt from retired KCS GP30s by Morrison Knudsen, Boise, Idaho.
b.	Equipped with 2,600 gallon fuel tanks, and pumping equipment to transfer fuel between slug and attached slug control units; sensing monitors activate the pumps to keep fuel level equalized between the control units and the slug.
c.	All three road slugs operate with UP GP40-2 slug control units.
d.	Renumbered to UPY 927-929.

Road Slug Model S3-3BDE — 1 unit
B-B trucks; 280,000 pounds operating weight

Road Number	First Number	Rebuild Date	Rebuilt From	Date Retired
(UP S310)	SP 1600	1 May 1980	UP U25B 634	25 Jul 2000

General Notes:

a.	One unit to UP at merger, numbered SP 1600.
b.	SP 1600 built by Morrison-Knudsen from UP U25B 634 (retired by UP in September 1972, sold to MK in August 1974) as a prototype for SP's own planned road slug program; the MK rebuilding included new step wells and a new low carbody, with new sand boxes and extra ballast.
c.	Equipped with 2900-gallon fuel tank and pumping equipment to transfer fuel from the slug and the attached control units; sensing monitors activate the pumps to keep the fuel level equalized between the control units and the road slug.
d.	Former SP designation was TEBU (Tractive Effort Booster Unit).
e.	Equipped to operate with former SP 7940-7959 group GP40-2s (built in April and May 1980) and former SSW 7960-7966 group GP40s (rebuilt in 1981 and 1982).
f.	Stored by UP at North Platte, Neb., during late 1998.
g.	Assigned UPY 930, not renumbered prior to being retired.

Road Slug Model S3-2B — 10 units
B-B trucks; 280,000 pounds operating weight

General Notes:

a.	Original total of 13 units; 10 units went to UP at merger; SP retired three units (SP 1603, 1604, and 1607) prior to the merger.
b.	SP's road slugs were rebuilt by its Sacramento shops from the road's own retired U25Bs.
c.	Equipped with 2900 gallon fuel tank and pumping equipment to transfer fuel from the slug and the attached control units; sensing monitors activate the pumps to keep the fuel level equalized between the control units and the road slug.
d.	Former SP designation was TEBU (Tractive Effort Booster Unit).
e.	Equipped to operate with former SP 7940-7959 group GP40-2s (built in April and May 1980) and former SSW 7960-7966 group GP40s (rebuilt in 1981 and 1982).
f.	SP 1601, 1608, 1609, 1613 stored by UP at North Platte, Neb., during late 1998.
g.	UP S319 (ex SP 1612) was the first of this group to be repainted to Union Pacific, completed on 18 September 1997.
h.	Renumbered to UPY 931-938.

Notes:

1.	SP 1602 was sold to National Railway Equipment on 28 April 1977.
2.	SP 1610 was sold for scrap to Louisville Scrap, 28 February 1998.