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Locomotive Phases - GE U23C, U30C, U33C, U36C

The GE Universal series entered production in 1956, with the first road switcher, the U25B, introduced in 1959, and the first six-axle unit, the U25C, introduced in 1963. 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 U30C started production in 1966 as an evolution of the previous U28C, initially sharing the same carbody. A slightly more powerful model, the U33C, was introduced shortly afterward, incorporating wider radiators and a redesigned rear hood section (the latter of which was adopted for the U30C at the same time). Unlike with previous horsepower increases, the U30C was not discontinued when the U33C was released, and in fact the U30C proved to be the best-selling six-axle model of the series. In 1968, GE introduced the U23C, a 12-cylinder, a medium-horsepower variant distinguished by six (rather than eight) tall engine-room doors per side. In 1971, the U33C was uprated to create the U36C, but unlike with four-axle models, the U33C remained in production thereafter.

Concurrent four-axle Universal models were shorter but visually very similar, with the only major difference in the hood being about 7 feet of mostly empty space behind the cab on six-axle units.

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 2a1. Most Phase 2b 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, although many 6-axle units were already built without them. 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 U30C and U36C were respectively replaced by the C30-7 and C36-7.


These phases are based on the U30C 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 U30C spanned all phases; the other models were all Phase 2a or later.

Four-axle models underwent a very similar (but not identical) series of evolutions; see GE U18B, U23B, U30B, U33B, U36B Phases.

Phase 1a 1b 1c 2a1 2a2 2b 2c 2d 2e 2f 2g1 2g2 2g3 2h1 2h2
Dates 1966-11 -
1967-01 -
1967-06 -
1967-12 -
1968-03 -
1968-06 -
1969-07 -
  1970-04 -
1971-02 -
1973-02 -
1974-01 -
1974-04 -
1974-11 -
1975-05 -
Radiator intakes Long, flush with hood Shorter; two doors with smaller intakes added Corrugated, raised from hood, fewer bolts on edges (appeared on some Phase 2b units)
Exhaust stack Tall Short
Brake chain pipe Square Cylindrical
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 2a1 2a2 2b 2c 2d 2e 2f 2g1 2g2 2g3 2h1 2h2
Handrail stanchion spacing Even Uneven Narrowed on right side (due to rearward battery boxes)
Left-side equipment doors 8 6 (inconsistent in Phase 2b)
Pilots Built-up area around MU boxes Flat around MU boxes
Air reservoir supports Gap between outer support and fuel tank support Slanted plate added between outer support and fuel tank support (possibly present on Phase 2e units)
Corner handrails Short notch in stepwell, handrails extend lower on pilots than stepwells Full-height notch
EvenHandrails extend to even height (inconsistent)
Cab headlight Rectangular casing Oblong casing External headlight, hinged numberboards
Cab drip rail Yes No
Phase 1a 1b 1c 2a1 2a2 2b 2c 2d 2e 2f 2g1 2g2 2g3 2h1 2h2
Left hood doorsHood doors behind the cab on the left side, excluding U23C
2-2-1 grouping; latches on 2nd, 3rd and 5th doors 2-1-2 grouping; latches on 2nd, 3rd and 4th doors
Battery box covers Tall, narrow, 6 x 4 bolts Shorter, wider, 5 x 3 bolts Moved rearward
Door latches Circular
SquareAppeared on a few Phase 2f and 2g1 units
Water level sight glassOn the right side of the hood under the exhaust stack
Yes No
Cab door stiffener No Yes
Steps 23" wide 24" wide, taller kick plates
Phase 1a 1b 1c 2a1 2a2 2b 2c 2d 2e 2f 2g1 2g2 2g3 2h1 2h2


Biel, C. Burlington Northern Motive Power Roster. Retrieved December 2019 from

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.

Sarberenyi, R. GE's U23C - Original Owners. Retrieved September 2017 from

Sarberenyi, R. GE's U34CH, U36C, U36CG - Original Owners. Retrieved September 2017 from

Strack, D. (2015). UP Diesel Roster, 1934-2009, Part 39. Retrieved December 2019 from

Thompson, D. GE's U30C - Original Owners. Retrieved September 2017 from

Thompson, D. GE's U33C - Original Owners. Retrieved September 2017 from