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The Southern Pacific AC4400CW

Southern Pacific’s final and largest order for diesel locomotives was for it’s fleet of AC4400CWs from General Electric. 279 locomotives, numbered #100 to #378, were purchased for delivery in 1995. There was a follow on order for 3 AC6000CWs, but the merger with Union Pacific intervened. Some say UP took the order, but according to Southern Pacific Diesel Locomotive Compendium, Vol. 2: Post-1965 SP and Cotton Belt Numbers, Union Pacific Transition by Joseph A. Strapac, the order was canceled.

Although constructed in a relatively short timeframe, there are some important differences in the locomotives produced:

1. The first 100, #100 – #199, lacked Locotrol radio control equipment. The rest, #200 – #378 had master/slave Locotrol, for use as Designated Power (DP), a modern form of helper operation. This manifest itself with extra radio antennas on the roof. 2 for #100 – #199 (voice communication and End of Train (EOT) monitoring), and 4 for #200 – #378 (2 additional antennas for the Locotrol). A key feature of DP is that a locomotive can switch between being a “master” or “slave,” and doesn’t need to be a dedicated “master” or “slave” as the older Locotrol units are (the #8300 series SD40T-2 snoots and the 4 GP40Xs, for instance).

2. Initially, #100 – about #300 were equipped with 4 snubbers on each truck, mounted externally to first and last axle. GE did some testing and decided it didn’t need the snubbers on both sides. The higher numbered units were built without the snubbers on the Fireman’s side front truck, and Engineer’s side rear truck were eliminated. This was retroactively applied (removing the snubbers) on earlier units built with all 4 snubbers per axle, leaving the mounting brackets in place.

3. Later units (approximately #302 and higher) were equiped with an extra box behind the inverter cabinet.

Athearn produced the first plastic model back in the early 1990s that retailed for $32.50 and built in the US. Details were typically bare for the time, but Details West produced many detail parts specifically for this model. This is known as a “Blue Box” Athearn because it arrived in a blue box, and required some assembly. This consisted of assembling steel handrails to metal stanchions, and pressing them into appropriate holes in the body. The locomotive was equiped with the X2F “Horn Hook” coupler that everyone hated.

A fundemental problem with this model is the too short nose. Clyde King has suggested cutting the nose and splicing 0.060″ styrene to lengthen it. However, with the beveled sides, this requires some ingenious body work.

Athearn AC4400CW Cab extension

The model also had relatively crude radiator grills, but, again, Details West offered parts that addressed this issue.

Note the smooth cab roof of the original “blue box” AC4400CW. Athearn retooled the cab roof in order to add the (prototypically correct) roof pattern, but failed to retool the length of the nose!


Athearn AC4400C cab retooled with pattern on roof. Small antenna is for End of Train (EOT) device monitoring. Large Sinclair antenna is for voice communications. Note grab irons added to nose!

Kato soon introduced it’s own AC4400CW in HO, but the model included trucks that were only suitable for early Chicago Northwestern prototypes. About 2004, Kato revised the model with later Hi-Ad trucks, similar to Athearn and as used by Southern Pacific. The problem was that the snubbers and brake cylinders were molded on rather than separate pieces, so they look a bit clunky close up.

Coming back to Athearn, in 2003, Athearn released the AC4400CW as part of its Ready to Roll (RTR) line. Production had moved to China, and with it, more roadname-specific details were added, paint was upgraded including many more safety decals omitted from the original blue box paint, and fine/flimsey plastic handrails were installed. Plastic McHenry couplers, clones of the Kadee couplers everyone likes, are now standard. The short nose and crude radiator grills remain.

I bought a recent run Athearn RTR line AC4400CW as #136. I had high hopes that Athearn might have done something to address at least the cab length issue, but alas, it’s the same old $32.50 locomotive gussied up in the Chinese factory and a $119.95 price tag.

After getting over the initial disappointment, it was time to decide how to build a better AC4400CW. I should note that most of the model is outstanding. It’s just that when it comes to the cab and the upper radiator grill work, it’s like two different model makers built the dies.


Fireman’s side, Athearn AC4400CW (click on image to enlarge)

The inverter doors behind the cab are accurate for a Southern Pacific model. The lack of the extra box behind the inverter box is accurate for locomotives #100 to about #302, although the box is available from Details West for later AC4400CWs in the order. The trucks are interesting. On the rear, you see the snubbers as they should be. On the front, the snubbers are missing as modified (see above), but the top bracket should remain, and thus is missing. I believe this is an error, but the short nose on the cab is a bigger “miss.”

So the first question I had was “what about the Kato?” Lets look at the shell, same angle as above:


Fireman’s side, Kato AC4400CW (click on image to enlarge)

The nose is much better. See how much closer it is to the stepwell? But there are other problems. Instead of the doors on the inverter cabinet, we have an array of “X panels.” That might be correct for a later AC4400CW (possibly UP AC4400CW-CTE #5700 – #5900 – CTE standing for Computerized Tractive Effort), but not any of Southern Pacific’s. The change from access doors to access panels may also reflect  a change in inverter type (from GTO to IGBT – click here for a discussion). That would be tough to correct. Perhaps filing and/or sanding off the access panels, and fabricating doors from 0.005″ styrene.

Compare the equipment blower filter box air intake – the farthest back part of the raised hood “box” behind the cab, and in front of the horn. The grill and the “X-panel” are reversed. Again, this might be correct for a later AC4400CW (again, possibly the AC4400CW-CTE ), but not any of Southern Pacific’s. It’s another tough modification, as there are no “X panels” or grills available as aftermarket parts.

This also has the extra box behind the inverter cabinet, but it is a separate piece and removable. This is accurate for later SP AC4400CWs, ~#302 and higher.

Things are similar on the other side, in the auxiliary cab (dynamic brake portion of the hood, behind the cab on the engineer’s side). Here’s the Athearn:


Engineer’s side of cab and dynamic brake portion of hood. Athearn AC4400CW (click on image to enlarge)

and here’s the Kato:


Engineers side of cab and dynamic brake section of hood, Kato AC4400CW (click on image to enlarge)

Again, the Athearn shell matches the Southern Pacific AC4400CWs, and the Kato is for something else (possibly an AC4400CW-CTE, as mentioned above). “X panel” access panels replace doors.

Now lets compare the top radiator grills. This, to me, is an important detail, as we look at our models from above a lot. Here’s the Athearn:


Upper radiator grill, Athearn AC4400CW. Note splice and frame around edges. (click on image to enlarge)

And let’s compare to the Kato:


Upper radiator grill, Kato AC4400CW. Note lack of frame around edges. This is more prototypical, and the grill work is much more detailed. (click on image to enlarge)

There is so much more detail on the Kato, and look at the periphery! The detail on the Kato goes right to the edge.

Another difference is the front door on the cab. Athearn, like the Southern Pacific, has a window in the access door. Kato does not, but Details West has a part to fix that.

I’d love to graft the parts Kato did better onto the Athearn. The Kato cab and radiator grills are so much better than Athearns! There’s another option to consider, and that’s grafting the Atlas Dash 8-40BW parts onto the Athearn AC4400CW. I’ll have more to say about that when the Atlas parts arrive.

Special thanks to Sean Graham-White and Mike Johannessen for research assistance and corrections to the original article.

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