Thanks for all the input. I had forgotten about the older UP Northerns, which are probably mostly the same as far as the shell connections go, just sans the monstrous split frame. Plus they at least have an "updated" pancake motor, instead of this one that just spins inside the frame, like a giant tyco powertorque drive. The newer pancake motors I have seem to work just fine, as my old fingerprint-tarnished chrome Santa Fe F9 still runs smooth as ever.

The club fell apart several years before I went to college, so that's one resource I don't have anymore. I had asked the same question of the guys over at the Tyco Collector's Forum where I've been active for a while, as some of them are rebuilding masters. (You have to be with Tycos!) They turned up an old article from the May/June and July/August 1986 Model Railroading magazines about fitting can motors in the old Northerns, but the process requires milling the frame out so everything fits, something I didn't have the time or tools to do. It could be of use to anyone else wishing to save an old Northern:

http://www.tycoforums.com/tyco/forum/topic.asp?TOPIC_ID=7703

The article is down at the bottom of the thread. Happy Model Railroad Preservation! 

I have a very old Bachmann CB&Q 4-8-4 in a white and yellow box that seems to be on its last legs. It runs slowly, and makes all kinds of whining noises. I would send it in for a replacement, but there are a couple of catches: first, it was given to me by one of the kindest members of our local train club not long before he died around ten years ago, and he did a beautiful job of weathering on it while it was his. Second, I like the CB&Q scheme better than any currently available, even if it is not an accurate CB&Q loco.

I have done as much maintenance as I can on it, and have checked the axles and found no cracks. I believe the problem is that the pancake motor is worn out, even after a thorough cleaning of the contact strip and a bath in rubbing alcohol to remove dirt from the armature. One of the Bowser repower units would be a perfect solution, but they stopped making them before I had the money, and the remaining stock seem to be in the hands of professional rebuilders who want $150+ for the service.

My question is this: I just found that many of the chassis parts for the new 4-8-4 are available in the parts store online. Is it possible to assemble a new chassis from these that I could shoehorn the old shell onto? (I've recently been building HOn30 steam locos out of N scale power, so shell attachment modifications are no problem for me.) And would it be possible to wire it to run on DC, as I don't have DCC and don't plan on converting anytime soon?