Introduced: 1986 (Bachmann "white box" version) and 1995 (Spectrum version)
As is generally the case with Bachmann's stable of "trainset crap" locomotives, there have been a couple of different versions of the SD40-2. The initial release came packaged in the generic Bachmann "white box". The second version came in Bachmann "Spectrum" packaging (a plastic clamshell inside a white cardboard sleeve).
The original 1986 mechanism is fairly typical of mid-1980s Bachmann design. It features a heavy, split-frame, all-metal chassis. The motor is a skew-wound, open-sided 3-poler. Ten of the twelve wheels provide pickup (with the remaining two wheels being saddled with traction tires). Current is transferred from the trucks to the chassis via oval metal contacts (IE, no wires). All wheels are geared, and all the gearing is plastic. Couplers are truck-mounted Rapidos. The wheels are low-profile, so no problems on Code-55 track.
Lighting on these first-run SD40-2's is pretty crazy. The shell is absolutely crammed with electronic gizmoage, all of which serves to provide directional lighting on either end of the shell, as well as (get this) a totally cheesy blinking light atop the cab.
Performance on these models is solid (if unspectacular). Throttle response is smooth and slow speed creep is decent (although a bit jittery at really low voltages). Pick-up is good (no problems through turnouts). They're a bit loud by modern standards though, and the top-end speed is overly high. My main gripe with these things though is the looks. The coloring schemes are ridiculously garish (see the UP example above), and the paint looks like it was applied with a trowel. And then there's the whole blinky light thing. Yeesh!
Circa 1995 this model was re-released under Bachmann's "Spectrum" banner. It featured a completely new mechanism and a slightly modified shell - and with "old blinky" having been (thankfully) given the heave-ho -
The chassis is new (still all-metal and split-frame, though) -
The motor is still open-sided and skew-wound (and now a 5-poler). The drivetrain is completely redesigned (now featuring flywheels). The worms are now actually part of the truck assemblies (and swivel right around with them on curves). All wheels now provide pickup (IE, no traction tires). The wheels are all geared (still) and all the gearing is all plastic (still). Similarly, the couplers are still truck-mounted Rapidos. All of the lighting control remains mounted inside the shell, although the directional lighting now comes courtesy of LEDs (rather than bulbs). And, as mentioned previously, the blinky light over the cab is gone.
Oddly enough, this new mechanism isn't much of an upgrade over the original. In fact, in many ways it's actually inferior. First off, it makes a heck of a lot more noise than the first version (barbershop razor syndrome - probably due to those crazy worm gears swiveling all over the place). Secondly, slow speed performance is iffy at best, what with jackrabbit starts having suddenly entered the equation. On the plus side, the top-end speed is much more reasonable. But jeez, who really cares?
The Spectrum shells are a little different. Although as far as I can tell, said changes basically boil down to a little less roof detail. I will say that the paint on the Spectrum models is much improved over the "white box" models (although it's difficult to imagine how it could've been any worse).
So, overall these are all pretty mediocre models (regarless of the version), and definitely typical of Bachmann's line of trainset dreck.
These models were ultimately discontinued circa 2004. They are no longer listed on Bachmann's website.
To remove the shell ("white box" version), gently pry the shell away from the four metal chassis pins (near the truck centers). The shell will then lift up and off.
For the Spectrum version, first unscrew the screw holding the fuel tank to the chassis. Once the fuel tank is out of the way, you'll see the two small screws that hold the shell to the chassis. Remove these and the shell should then lift up and off.
Grade: C (either version)
First release reviewed: 10/86 Model Railroader ("Bachmann's N scale version of this popular diesel is manufactured in Hong Kong and features a clean, straightforward design. To remove the body shell, spread the sides and lift up. The metal frame is made in two vertical halves separated by insulating spacers. Remove the screw at each end, and the mechanism falls apart quite neatly. The tiny double-ended, open-frame motor has a three-pole, skewed armature. The drive mechanism used in this unit is a new one to me. Rather than the usual gear tower with idler gears, the drive shaft angles down and by means of a plastic ball-type universal engages the hollow center of a plastic worm mounted directly on the truck. This worm engages the drive gear of the center axle directly. Idlers in the truck transfer the power to the other two axles. All the gears are plastic. I like this design. The trucks have considerably more freedom to swivel and pivot than is typical, so the locomotive tracks quite well. All 12 wheels are powered. The center pair of the rear set is equipped with traction tires.
"I found the engine's performance to be quite satisfactory. Its 1-ounce drawbar pull is equivalent to about 24 free-rolling cars on straight level track. The electrical system on this engine is also quite straightforward and efficient. A large one-piece wiper on each truck-frame half contacts the back of each wheel as well as the bottom of a frame half. My one objection to this system is that it looks a bit odd and out of place when the locomotive is viewed from the side... The locomotive scales out fine for length and wheelbase. The hood is about a foot wider than scale... More disturbing is the locomotive's height. It stands about a foot too high; unfortunately the place where that foot is located is quite obvious - the body rides high above the tracks, making the engine look odd from the side... The body appears to be nicely detailed, although to be catty about it, the paint is too thick and glossy, making it hard to tell... The Santa Fe scheme on my sample was incorrect in that the separation line between blue and yellow should go straight across the top, rather than be pointed, and the deck should be blue. High marks, incidentally, for the handrails. These are quite a bit nicer than we're accustomed to. In summary, here's a good performer with innovative engineering features. Despite the shortcomings on appearance, the price should make this engine very attractive to many N scalers. UP, SF, BN, Family Lines. $22")