Last updated October 16, 2008
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Trainiax --> Drawings --> Locomotive Phases --> 6-axle EMD Locomotives
Trainiax --> Info --> Locomotive Phases --> 6-axle EMD Locomotives
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| Locomotive Phases | 6-axle EMD Locomotives |
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SD7
No major production variations.

Other details: Units with steam generators have extra vents on top of short hood; units without have bare top of short hood.
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From SD7 to SD9
--Classification lights mounted at an angle at corners of hood ends, rather than flush and closer to middle
--Redesigned steps
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SD9
Phase 1: cast/fabricated handrail stanchions, 4 36" radiator fans
Phase 2: stamped handrail stanchions, front left ladder replaced by single grabiron
Phase 3: 2 48" radiator fans
Phase 4: Higher battery boxes (raising cab and short hood)

Other details: Units with steam generators have extra vents on top of short hood; units without have bare top of short hood.
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SD40 (US-built)
Phase 1a: 1966-- button-top fans, flat battery boxes under cab (some ribbed), top-mounted nose grabirons, handbrake in nose, low-mounted brake cylinders on trucks
Phase 1b1: 1966-1967-- ribbed battery boxes under cab, handbrake at rear of hood
Phase 1b2: 1967-- 1 high/3 low brake cylinders on trucks
Phase 1c: 1967-- open-top fans
Phase 2a: 1967-1968-- high-mounted brake cylinders on trucks, electrical cabinet box
Phase 2b: 1968-1971-- drop-mounted nose grabirons
Phase 2c: 1971-- longer dynamic brake taper, ribbed equipment blower duct

Other details:
--Phase 2b1/2b2 are not distinguished in drawings.  Phase 2b1 has chickenwire radiator intake subscreen; Phase 2b2 has square grid subscreen.
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From late non Dash-2 to early Dash-2:
--Frame length increased from 65' 9-1/2" to 68' 10" (Note: The locomotive frame was lengthened to accomodate the new and longer HT-C trucks while still maintaining a 4000-gallon fuel tank.  HT-C trucks have all traction motors oriented in the same direction, creating an overhang over the innermost axle that makes each truck 1 1/2 feet longer than the earlier Flexicoil.

--Bolted (rather than hinged) front battery boxes
--Oblong water-level sight glass (right rear of hood)
--Modified central air intake and blower duct
--Modified rear hood doors
--Lengthened walkway blower duct
--Bolted, rectangular cab side panel
--Enlarged electrical cabinet box
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SD40-2 (US-built)
Phase 1a: 1972-1975-- chickenwire radiator intakes, 81" short hood, ratchet handbrake, bolted cab side panel
Phase 1b: 1976-1977-- 88" short hood (except early Phase 1b), corrugated radiator intakes
Phase 2a: 1978-- wheel handbrake (appeared on some late Phase 1b), new jacking pads, new electrical cabinet box, new battery box hinges
Phase 2b: 1978-1979-- welded cab side panel
Phase 2b2: 1979-- flush exhaust stack
Phase 2c: 1980-1981-- Q-type fans
Phase 3: 1983-1984-- new blower duct, straight frame profile

Other details:
--BN units were built with hinged (rather than bolted) front battery boxes through all production.  UP units were retrofitted with similar hinged battery boxes after production.
--CR units were built with Flexicoil trucks in place of HT-C trucks.
--ICG and MP units were built with additional jacking pads next to the stepwells.
--NW units were built with triple-clasp brakes.

The following details vary between units of all phases:
--The right side notch in the sideframe over the air reservoir ends either at the 7th handrail stanchion (ahead of left side notch) or between the 7th and 8th handrail stanchions (equal to left side notch).
--Emergency fuel cutoff is either ahead of or behind the 2nd handrail stanchion.  The surrounding sideframe is either straight or extended in a small downward notch.
--Dynamic brake blister may or may not have a hatch ahead of the main intake.
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SD40-2 (Canadian)
Phase 1a: 1972-1975-- chickenwire radiator intakes, louvers at rear of hood
Phase 1b1: 1977-1979-- corrugated radiator intakes, new battery box hinges, new electrical cabinet box, no louvers at rear of hood
Phase 1b2: 1979-- winterization hatch, new truck bearings
Phase 2a: 1980-1982-- flush exhaust stack, Q-type fans, new jacking pads, front anticlimber, no winterization hatch
Phase 2b1: 1982-1983-- new blower duct, altered handrail stanchion spacing, winterization hatch
Phase 2b2: 1983-1985-- straight frame profile
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SD40-2W
CN was the only buyer.  Cab shared with GP38-2W and GP40-2W; dimensions and most other details shared with standard SD40-2.

Phase 1a1: 1975-- dynamic brakes, chickenwire radiator intakes, circular sand hatches, single-loop brake chain, single louver set under short rear hood door, dipped handrail behind cab
Phase 1a2: 1976-- no dynamic brakes, rectangular sand hatches, brake wheel moved forward, two louver sets on tall rear hood door
Phase 1a3: 1978-- dynamic brakes, double-loop brake chain
Phase 1b1: 1979-- dynamic brakes, straightened handrail behind cab, new jacking pads
Phase 1b2: 1980-- dynamic brakes, winterization hatch
Phase 2: 1980-- no dynamic brakes, winterization hatch, corrugated radiator intakes, flush exhaust stack
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SD40T-2 (consistent with US-built SD40-2)
Phase 1a: 1974-1975-- 81" short hood (D&RGW version), ratchet handbrake, bolted cab side panel
Phase 1b: 1977-- 88" short hood, wheel handbrake, new battery box hinges
Phase 2a: 1978-- new jacking pads
Phase 2b: 1978-1979-- welded cab side panel
Phase 2c: 1980-- flush exhaust stack
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SD45T-2
Details are consistent with Phase 1a US-built SD40-2 and SD40T-2.

Other details:
--Phase 1a1 (1972-1973) has standard jacking pads, no front anticlimber and no air conditioner on cab roof.
--Phase 1a2 (1974) has air conditioner.
--Phase 1a3 (1975) has front anticlimber.
--Phase 1a4 (1975) has new jacking pads.
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SD50
Phase 1: Notched frame profile, flat/ribbed blower duct, angled inner dynamic brake housing
Phase 2a1: Straight frame profile, angled blower duct, new exhaust stack
Phase 2a2: New handrail stanchion spacing (middle stanchions moved forward)
Phase 2b1: Old handrail stanchion spacing, straight inner dynamic brake housing, higher dynamic brake intake
Phase 2b2: New handrail stanchion spacing
Phase 2c: Air reservoir moved rearward

From SD50 to SD60:
--Eight access doors under radiators (rather than six)
--First two hood doors (under exhaust stack) widened
--Blower duct/raised handrail section on left side behind cab moved forward
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SD60
No major production variations.  A very subtle difference between some units is the 4500 vs. 4800 gallon fuel tank, with a difference in length of only a few inches.
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SD60M, SD60I
Phase 1a: Three-piece windshield, single set of louvers under left side of cab, angled hood seam behind cab, bolted square panel under right side of cab
Phase 1b: Three sets of louvers under left side of cab
Phase 1c: Dynamic brake intake and fan moved forward, order of hatches over intake reversed, vertical hood seam behind cab, latched square panel under right side of cab
Phase 1d: Short hood beveled downwards on top front corners, straight raised walkway on left behind cab
Phase 2a: Two-piece windshield
Phase 2b: No raised walkway on left behind cab

Other details:
--Seven access doors under radiators (instead of eight on SD60) to make room for rear-mounted handbrake
--Inclusion of nose door window varied both throughout production and over individual units' lifespans
--Phase 2a and 2b produced concurrently
--SD60I ordered by Conrail only; identical to Phase 2b SD60M except for isolated cab
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SD70M vs. SD70MAC
--Overall length increased from 72' 4" to 74' (Length increase visible in gap between fuel tank and rear truck; hood extends beyond rear radiator intakes)
--Different central air intake area
--SD60-style blower duct (compared to simple box style on SD70M)
--Raised walkway on left side (not on SD70M)
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SD70MAC
Phase 1a: 4 steps, HTCR Ia trucks, horizontal electrical cabinet box, straight end handrails, 2 foremost engine compartment doors, cab headlight
Phase 1b1: 5 steps, end handrails bent outwards
Phase 1b2: vertical electrical cabinet box
Phase 1c: HTCR Ib/HTCR II trucks, 3 foremost engine compartment doors
Phase 2: canted radiator intake

Other details:
--Isolated cab introduced partway through Phase 1b1 production (SD70MAC-I designation)
--Nose headlight introduced on late Phase 1c BNSF units
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Michael Eby 2008