Here is an explanation of how to disassemble and assemble the AMT/KMT aluminum passenger cars, obtained online some time ago. Note some cars have a 3 piece body (separate sides and roof that slide together), but most seem to have a one piece roof and sides extrusion. The passenger cars and F7 diesels from these companies are among the most treasured parts of my train collection.
CNW Don
Disassembly of an AMT/KMT aluminum passenger car:
*Turn the car over and you'll see 4 slotted screw heads in the corners.
Those need to come out.
*Once they're out grab the trucks on one end and pull up, then do the same on the other end. The skirts at the ends of the body are curved in - tilt the entire frame to one side and the chassis and trucks should come out (You'll need to gently pull a car side out a little to free the chassis - don't use gorilla power force, but you'll have to pry a bit).
*If the car has never been opened there should be 2 plastic doors that slide into the cast car ends. Slide those out, and then remove the single screw holding each car end in place. The ends are in a channel, and you'll have to wiggle them a bit to listen them up - they'll slide out, but they're a tight fit.
*If the shell is a 3 piece type the roof will slide off of the sides. To reassemble, just go backwards with the steps above.
The bulk of cars disassemble like that, but cars like the baggage and combine are a little more involved. When you reassemble those the sliding doors a real pain to keep in place.
*There's a tiny channel that the top part of the door slips into - no sweat there, but when you go to put the chassis back in place you have to get the bottom of the doors lined up, keep the doors in place to get lined up in the chassis' channel, and then push the frame in. Not for the faint of heart - you'll never get 'em on the first try. Big Grin
Put a piece of scotch tape across the back of the door door and car side to hold the door in place on the inside of the shell (leave a small gap between the door and the door opening so you can remove the tape after the floor is back in place). Don't get the tape on the blue plastic or white translucent window strips as you might pull them loose.
The wiring on these is usually pretty brittle - rewire with a good quality, flexible wire (the wire used for rewiring Lionel roller assemblies or whistle tenders works fine). The bulbs have a tendency to wiggle loose as they're screw base types. Make sure the bulbs are screwed in snugly. Test the bulbs to be sure they work (they came with good old made in the USA GE bulbs that are pretty durable). If they light up, here's a trick to keep them shining - get a bit of clear nail polish, then place a tiny drop of the polish onto the brass base of the bulb and the cast in socket in the chassis. Let it dry, and then reassemble the car as above. The bulbs won't wiggle loose during running, but will come out with a twist when it's maintenance time...
Hmmmm - that looks like something I may have typed up at one time (all those brackets look familiar)... 
