Here is a video of the issues I'm running into attempting to pull this beasty apart!
Hi Robert,
I've pulled a few of these apart, so let me offer a few observations. The bottom plate is only prevented from lifting out by the wires from the chuff fingers, that you identified on your video. Just pull it straight up. It is possible to break it at the joint where the vertical piece meets the horizontal but last time I looked they were available from Bachmann:
Loco Underframe Brown ( Large 2-6-0 ) [G814X-00T04-87] - $35.15 : Bachmann Trains Online Store!
The fingers for the chuff are attached to the upper portion of this base. Here's a photo of the base almost removed, and the chuff plate is arrowed. You may not be able to get it further out than that due to the wiring from the chuff. The PCB with the 2 orange LEDs is the firebox flicker. I ignored it. The chuff plate wiring just leads out the back to the connector under the tender front. (Marked "sound wiring" on the Bachmann drawing.) You might try pushing the chuff wires from the back of the cab further in to the loco to free them up a bit? On your video there are 2 pairs of wires coming from under the chuff drum/axle, which are not standard - push them further in to the loco and that might free up the chuff plate a bit!
Here's a pic of the bearings and wires after the axles came out. You don't need to do this unless your gear is cracked. At the top is a bearing with 2 white wires and the bottom has 2 green ones. (You can also see the holes that fit the springs under the bearings - on top when it is right-way up!)
The circuit board on the back of the motor is, I believe, for DCC interference suppression. I think I have read that you can remove it. Greg?
I did manage to fix mine without buying a new one. Here's the pic of the small bracket I made and glued and screwed to the bottom plate.
On this photo you can also see the electrical connections to the hornblocks/bearings. I imagine yours have been snipped as I don't see any on your video. What you have to do is wire the 2 pairs of bearings together and then lead the wires up into the boiler to connect with the main PCB. Or, if you can't get that out, wire them direct to the motor.
Under the blocks/bearings is the spring. Here's one that wasn't replaced correctly:
You can lift the wheel gently and replace the spring with a pair of tweezers.