The 2106 motor/truck assembly is available from Bachmann's parts website for $10.00 plus shipping.

http://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=66_68_91&products_id=4398

Hardly an expert, as I too am new to model railroading. When I got back into it, I also faced the coupler dilemma, and decided to go ahead and replace all of the horn-hook couplers with the prototypical knuckle couplers. The existing couplers on my inventory of locomotives and rolling had every conceivable mounting method, so a bit of patience and a lot of research was necessary. Some replacements are easy and some quite difficult, but I enjoyed the challenge of reengineering the various coupler mountings.

As others have mentioned Kadee is probably the best source of coupler conversion parts and information, but Bachmann (EZ Coupler) and McHenry (Athearn) also have knuckle coupler parts and information as well. Links to each of their websites are below. Note that the Kadee site has documented the conversion process (along with their coupler part number) for many, many old locomotives and rolling stock.

Yet another option that I considered was keeping a "hybrid" coupler arrangement. Replacing a horn-hook coupler on one end of a car created a "transition" car that could successfully connect both coupler types in a consist.

Others have suggested a good hobby shop as a source of information, and you may have success with that, assuming you are near a good shop. Those that I encountered had little knowledge of coupler replacement, and were more interested in selling me new locomotives and rolling stock, with which I was not interested.

Good luck and have fun with your "project."

Kadee:
http://www.kadee.com/conv/hocc.htm

Bachmann:
http://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=66_68_91&products_id=5885

McHenry:
http://www.athearn.com/Search/Default.aspx?CatId=THCC

Hard to tell the "vintage" without more information. But if it is marked "Bachmann Hong Kong" or "Bachmann China" on the bottom, it most likely uses what a previous reply mentioned as the "pancake" motor. If so, parts are available on the Bachmann site.

Go to:
Parts, Service, & Information
Order Parts
HO Parts
Universal HO Parts

A dummy truck is available: Dummy Truck (Older 4 Wheel Drive Diesels) (HO), Model: H112X-2105
A truck/motor assembly (pancake motor) is  available: Motor & Truck Assy (HO Older 4 Wheel Drive Diesels)(Universal) Model: H112X-2106
The lamp bulb is also available: Old Style Light Bulb (N & HO Scale), Model: PN-9884

The truck/motor assembly (@ $10.00) would take care of a motor or drive gear issue (and the assembly includes new traction tires) and the dummy truck (@ $6.50) on your locomotive may not need replacement. I just rebuilt two of these (Santa Fe War Bonnet shells) and they now run like new. Granted, as suggested in other replies, new locomotives feature significantly better "engineering" with much improved motors and smoother performance, but there is also a certain satisfaction that can be achieved with the successful rebuild of a "vintage" piece of equipment.

Good luck.

Here is a link to the two GE-U36 versions I have encountered.
http://www.gsitconsult.com/images/geu36.pdf

I really wish to keep both units as original as possible, and have had no problems getting the so-called "pancake" motor in other locomotives to run quite smoothly and properly.
My goal here is to learn as much as possible about the Bachmann "engineering" of these two versions.

As I said in the original post, this motor is still readily available from Bachmann, but only in the dual drive/pickup configuration (as in the lower photo in the above link).

With a renewed interest in model railroading, I have been having much fun rebuilding (or trying to) diesel locomotives. My current project involves two GE-U36 engines (Santa Fe #350, "pancake" motor), one marked Bachmann Hong Kong and one marked Bachmann China. The Hong Kong version uses a front truck pickup, with rear truck drive without pickup (only two motor terminals, connected via a top "bus" to the front pickup). The China version uses the same front truck pickup, but the rear drive truck also has pickups (four motor terminals). I purchased a new truck/motor assembly from Bachmann, and upon inspection have noted that it too has both drive and pickup functions (four motor terminals).
Could anyone perhaps clarify these two configurations or offer advice on upgrading the apparently older "front pickup only" version to the newer front/back pickup configuration.
I have searched for some kind of wiring diagram without success. Thus, any information would be greatly appreciated.
(I tried to post two small photos of the different configurations, but this messaging system reports "upload folder full...contact administrator" which I will attempt to do.)
Jeff Anderson
West Des Moines, IA

Thanks to each of you for the information. Being kind of new to model railroading, all the help available is so greatly appreciated.
Jeff A

I am trying to determine if the currently being sold "Bachmann EZ-Track Rail Joiners: (Bachmann HO 44499 EZ Track Rail Joiners 36 per card) are unique to EZ Track or if they will also work with original Bachmann HO track (i.e. vintage early 1990s without roadbed).
Could anyone offer an answer? Thanks so much...