2-6-0 troubleshooting

[2ManyHobbies]

I was adding weights to my 2-6-0 and metal wheels/axles for my cars today to see if I could get it to climb better. Towards the end, the engine just refuses to move now. All the DCC functions work for the most part (light won't turn on but I think it has been that way for awhile) so I know the address is working. Tried removing the last weight and didn't make a change. Tried a different section of track, nada. Cycled power to the DCC controller twice (once with the switch, again with with unplugging it), nothing.

Progression:

• Tested train with no weight
• Added weight up front, made improvement but caused nose to drag
• Added weight to rear of engine, made more improvement
• Replaced plastic axles with Bachmann metal axles. Seemed to add drag (cars did not roll as good). Ran engine for a few minutes with cars to see if the new axles needed "break in" cycle
• Added additional weight to rear of the engine. Engine no longer moves but still has sounds.

I have read that the plastic gears can break inside but I'm unsure how to take this darn thing apart to see what is inside. There are 3 screws midway on the bottom of the engine, another screw up front for the two front wheels, and 3 in the back of the engine for the tender connection wire and coupler. I see nothing on top as far as how to remove the top of the engine. I have removed the tender connection multiple times to gain better access to the rear of the engine.

Before I start removing stuff, I was hoping someone has a guide of some sort showing how this comes apart. Online wasn't a whole bunch of  help as it seems videos show trains with screws in places I don't have screws.

[rbturner]

How were you adding the weight to the loco?