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Locomotive Descriptions and Phases - GE U18B, U23B, U30B, U33B, U36B

The GE Universal series entered production in 1956, with the first road switcher, the U25B, introduced in 1959. By the late 1960s and early 1970s, several models were available that all followed a common design, with only a few differences to account for varying engine sizes and frame lengths.

The U30B started production in 1966 as an evolution of the previous U28B, initially sharing the same carbody. A slightly more powerful model, the U33B, was introduced shortly afterward, incorporating wider radiators and a redesigned rear hood section (the latter of which was adopted for the U30B at the same time). All three models, along with the earlier U25B, were powered by a 16-cylinder FDL engine. However, unlike with previous horsepower increases, the U30B was not discontinued when the U33B was released. In 1968, GE introduced the U23B, a 12-cylinder, medium-horsepower variant that proved to be the most popular 4-axle model of the series; it was distinguished by six (rather than eight) tall engine-room doors per side. In 1970, the U33B was uprated and replaced by the U36B, and with the increase in horsepower provided by the FDL engine, the 8-cylinder U18B was added in 1973.

Four of the five models were 60' 2" long with 36' 2" truck centers; the U18B was 5' 6" shorter. Concurrent six-axle Universal models were longer but visually very similar, with a nearly identical hood with 7 feet of mostly blank space behind the cab.

GE made many gradual improvements to the Universal series during production, which were generally applied concurrently to all models. Many of these changes were not evident externally; for instance, GE made many improvements to the FDL engine and electrical system as horsepower was increased and reliability improved. However, some changes, such as wheelslip control, were readily visible. GE's early wheelslip-control system relied on axle alternators on every axle, which are present on most earlier Universal units. Later systems measured current-draw differences between the traction motors, eliminating the need for all but one axle alternator. Depending on railroad specifications, some later-production Universal units continued to use both systems.

Earlier-production units used oil-bath air filters, evident externally by a high-mounted intake below the front of the radiators starting with Phase 2a. Most Phase 2b1 and later units used paper air filters, which used a low-mounted intake (the same doors and intake flipped vertically).

Several changes in the early 1970's were the result of increasing standards or regulations. Footboards were forbidden on new locomotives starting in early 1975, and Universal locomotives were built without them starting in late 1974. Shortly afterward, GE widened the corner steps and raised the coupler cut levers to make them accessible from the steps. The external headlight and numberboard access panels at the very end of Universal production coincided with AAR Clean Cab concepts, where corners and hard edges inside the cab were minimized.

In 1977, a combination of significant updates led to the creation of the "1977 Series" or Dash-7 series of locomotives, and the U23B, U30B and U36B were respectively replaced by the B23-7, B30-7 and B36-7.


I've based these phases on the U30B roster compiled by David Thompson. However, I've found a few minor errors and a number of additional detail differences, so I've made the following changes:

Only the U30B spanned all phases; the other four models were all Phase 2a or later.

Six-axle models underwent a very similar (but not identical) series of evolutions; see GE U23C, U30C, U33C, U36C Phases.

Phase 1a 1b 1c 1d 2a 2b1 2b2 2b3 2c 2d 2e 2f 2g1 2g2 2h1 2h2 2h3 2h4
Dates 1966-11 -
1967-01 -
1967-07 -
1967-09 -
1967-09 -
1968-07 -
1968-10 -
1969-04 -
1969-09 -
1970-?? -
1970-06 -
1971-05 -
1973-01 -
1973-11 -
1974-11 -
1974-12 -
1975-03 -
1976-06 -
Radiator intakes Long, flush with hood; 5 staggered-height dynamic brake resistor grids Shorter; 2 doors with smaller intakes added; 3 dynamic brake resistor grids in an even row Doors and dynamic brake grids moved rearward Corrugated, raised from hood, fewer bolts on edges (appeared on RI Phase 2b2-2b3 units)
Brake chain pipe Cylindrical, curved Square, straight (as on U28B) Cylindrical, curved
Brake wheel Small Large
Exhaust stack Tall Short
Rear hood No break in hood width, section with intakes wider than hood, flush radiator outlets with raised walkway Entire rear hood widened to match radiator intakes, radiators raised to match roof walkway
Taper ahead of radiators No Yes No
Horizontal drip rail on radiators Below small rectangular hatches Above small rectangular hatches None (inconsistent) None
Phase 1a 1b 1c 1d 2a 2b1 2b2 2b3 2c 2d 2e 2f 2g1 2g2 2h1 2h2 2h3 2h4
Left-side air reservoir piping 90-degree joints curved
Left-side equipment doors 6 lower doors, box with 2 doors on top 6 lower doors slightly widened, no box on top
Handrail stanchion spacing Even Uneven (Except on left side of early Phase 2b3) Narrowed on right side (due to wider battery boxes)
Air reservoir supports Gap between outer support and fuel tank support Slanted plate added between outer support and fuel tank support
Pilots Built-up area around MU boxes, single low-mounted coupler cut lever (mounted higher on units with plow) Flat around MU boxes No footboards, double coupler cut levers (1)Single high-mounted coupler cut lever
Steps 23" wide; bolted step treads Welded step treads (inconsistent in Phase 2d-2e) taller kick plates 24" wide
Corner handrails Short notch in stepwell, handrails extend lower on pilots than stepwells Full-height notch Handrails extend to even height
Phase 1a 1b 1c 1d 2a 2b1 2b2 2b3 2c 2d 2e 2f 2g1 2g2 2h1 2h2 2h3 2h4
Cab headlight Rectangular casing Oblong casing External headlight, hinged numberboards
Cab drip rail Yes No
Left hood doorsHood doors behind the cab on the left side, excluding U23B
2-2-1 grouping; latches on 2nd, 3rd and 5th doors 2-1-2 grouping; latches on 2nd, 3rd and 4th doors
Door latches Circular Square
Water level sight glassOn the right side of the hood under the exhaust stack
Tall, narrow upper glass;
circular lower glass
Oblong lower glass None
Battery box covers Tall, narrow, 6 x 4 bolts Shorter, wider, 5 x 3 bolts
Cab door stiffener No Yes
FB-2 trucks Not available Brake lines routed below brake cylinders Lines above brake cylinders
Phase 1a 1b 1c 1d 2a 2b1 2b2 2b3 2c 2d 2e 2f 2g1 2g2 2h1 2h2 2h3 2h4


  1. Pilots, Phase 2h2: Double cut levers with no footboards appeared on some earlier units, such as SOU Phase 2g U23B's.


Davis, W. (2010). Wheel slip control in the General Electric Universal Series. Retrieved December 2018 from

Davis, W. (2014). General Electric's 1977 Series Locomotives. Retrieved December 2018 from

General Electric. Educational Manual, Model U33 Diesel-electric Locomotive. GEJ-3866, 1969-07.

General Electric. Operating Manual, General-Electric Diesel-Electric Locomotive. GEJ-3856B, 1972-06.

Heacock, D. J. (2012).GE U36B LOCOMOTIVES. Retrieved December 2019 from

Sarberenyi, R. GE's U18B - Original Owners. Retrieved November 2018 from

Sarberenyi, R. GE's U23B - Original Owners. Retrieved November 2018 from

Sarberenyi, R. GE's U33B - Original Owners. Retrieved November 2018 from

Sarberenyi, R. GE's U36B - Original Owners. Retrieved November 2018 from

Thompson, D. GE's U30B - Original Owners. Retrieved November 2018 from