This strange little unit is a "track geometry" car - used (on real railroads) to check for bad track. And unfortunately, it's one of the worst locomotives I've yet encountered in N scale (and hey, I own those old rubberband-drive Lone Star locos, so that should tell you something). These used to have the distinction of being the cheapest powered unit money could buy. I remember back circa 2000 when you could actually buy one brand new for ten bucks. And you know what? They're not even worth that...
The split-frame chassis is all metal. The motor is an open-sided 3-poler (a really cheap looking one, too). All gearing is plastic. Non-directional lights are mounted on either end of the chassis. No couplers and no traction tires. Current is transferred from the wheels directly into the frame - IE, the truck "sideframes" (where the wheels mount) are molded right into the chassis. The wheel flanges are reasonably sized, so no problems on Code-55 track.
The whole wheel situation is pretty strange. There are two axles with four normal sized wheels, and then three pairs of axles with really tiny wheels (two fore, two aft, and two in the center). The "normal" wheels all provide pickup. The center pair of tiny wheels are electrically neutral, whereas the pairs of tiny wheels on either end do conduct current - or at least they could if they were actually touching the rails!
Now, I'm told that this business of having the "tiny" wheels suspended in mid-air is, in fact, prototypical. Said wheels are only used when the unit is in rail-testing mode. Otherwise, they remain above the track. But, come on. If that's the case, why make them conductive? Or more importantly, why not make the four tiny wheels in the center conductive? At least those touch the rails! So anyway, the upshot of this whole rant is that you're stuck with a grand total of four pickup-providing wheels on this thing.
I've tried a few of these, and so far they all have the same major problems. First off, they make use of Bachmann's notoriously crappy "white plastic" gears (a curse that plagued most of Bachmann's locomotives of the 80's and 90's). And, as such, I've come across precious few of these models that didn't have some sort of gear problem (cracked, warped, missing teeth, whatever). And even the ones where the gears appear to be intact still run like hell - noisy, jittery, etc. Next is the whole pickup situation. Four wheels on the rails that conduct electricity? Well, good luck getting one of these diabolical little bastards through a turnout without it stalling. And lastly, derailing. Wow, these things do love to hop the rails. I haven't spent a whole lot of time trying to analyze the problem (what with all the other problems), but it appears that all of those weirdo tiny wheels, in addition to being useless vis'a'vis pickup, also tend to interfere with the business of actually trying to run this thing around.
So, basically a novelty (IE, a toy) that really has no business running on a model railroad.
This model was (thankfully) discontinued circa 2004. It is no longer listed on Bachmann's website. AFAIK it never received any upgrades or modifications over its entire production run.
To remove the shell, simply pry the sides apart and lift.