Thanks, I am researching and will soon buy a couple of replacement locos that are DCC ready or already installed. However, I like a challenge and am not afraid of electrical and mechanical retrofits. And since these are cheaper locos, I am not afraid to start the conversion and discover they have become shelf items that no longer work (or work very poorly). But at least I had the pleasure of learning and building my expertise!

Thanks again for the warning. Nice to be jolted with the reality of the task!

I have a locomotive that I got in the original Bachmann train kit "Thunder Valley". This is a DC version of the EMD GP40. I was thinking of trying to convert it to a DCC version using the NCE Z14SR decoder. Has anyone tried this?

Also, I got another old DC locomotive, a Bachmann EMD F9A (the older version with "Bachmann Hong Kong" stamped on the bottom). Can this be converted to DCC?

Looking at both units, I think I have to modify the chassis to accomadate room for the decoder. The EMD F9A looks like I also have to isolate the motor from the chassis?

What other things should I look for?

Yes, you will only be able to use the black box switch.
Be careful trying to hook-up directly to the green wires coming out of the switch. These are electromagnetic coils (essentially tiny wire wrapped on a spool) and if you provide continous power to these wires, you will burn out the coil and the automatic switch will NOT   work (or worse, it will melt stuff).
The black box that came with your switch hooks up to the AC power (red wires) from a transformer (Accessory output on the Bachmann DC controller). The three green wires hookup to the black box. When you flip the switch, the black box sends a short burst of power to "throw" the switch. Power is not on the whole time to the switch. In fact, you can manually switch the track back (using the little side lever on the track) and the black box switch does not have to be changed.
The link of the Lenz DCC switch controller allows you to get rid of the black box and wire directly to the green wires. Check to make sure that this DCC controller only sends "pulsed" output to the switch (it should indicate that it is specifically for twin coil switches).

My wife got me a bunch of n scale train stuff for Christmas! Love the wife for indulging me as well!

I got a bunch of turnouts and some of the crossovers, and all of them except one worked flawlessly.
http://www.bachmanntrains.com/home-usa/board/index.php/topic,22867.0.html

I discussed what I found in this forum. A little care and it works good and I have an extra screw

One other thing to look for is factory defects. I had multiple turnouts all of them worked well except one of them did not work correctly. It did essentially the same thing as yours (though I was running in DC only). If the locomotive went fast over the frog, it would go through. If I went slow, the loco would stall and I would have to nudge it.
I took the switch back apart to see what was wrong (be careful as the parts are held in by the backplate). When I removed the metal cover a screw fell out. I looked all over for the location of the screw and could not find it. I even took a known good switch apart and this extra screw was not in the other turnout.
I put everything back together (being careful to time the rack and gear, see Satnik's post link) and the turn out has worked flawlessly. To the best of my knowledge, the factory must of had an extra screw fall into the switch during assembly and was shorting out the frog?

skipgear, I have the same issue. When you say replace the trucks, how do you do that on locomotives? I understand on the rolling stock and have done it.

Thanks, I found out more history on other websites. But your explaination was more concise and easier to understand.
So I am going to look more closely at my couplers and shim them to the correct height so I can use them. But I will continue to research the knuckle type coupler.
Thanks again!

I have the 'Thunder Valley' starter set and a whole bunch of extra track that I have laid out with crossovers, switches, tunnels, bridge, and 4% grade. Everything in the set works well and I only had to fix one of the turn-outs (seems that the factory put an extra loose screw in the mechanism and was shorting out the frog).
Now I am shopping for more cars and got another Bachmann engine (F7 A unit). I got a box car on ebay and went to use it and found that the coupler does not work with the cars in this set. It appears like the couplers should work, but they seem to be at differing heights. The other loco seems to be compatible, but even these couplers seem to be different. I thought Rapido couplers were Rapido couplers??? Is there multiple styles? Would it be worthwhile to switch all rolling stock to some kind of magnetic knuckles? Is the EZ-Mate MarkII any good?

I am new here and new to model railroading, but I have decided to use EZ track for my layout. After investing in several crossovers and turnouts, I discovered that the little black boxes get to be rather tedious to use. I am still using DC but am working to convert to DCC. Here is what I am doing to the switch controllers to make them DCC controlled (I am going to take some video and post on Youtube).
1) I take the control box apart and desolder the slide switch. Use care to not damage circuit or solder pads.
2) Solder in wires in place of the switch. It appears that the switch is a DPDT switch so I am putting six labeled and color coded wires onto the circuit.
3) I put the wires out through the switch hole and reassemble the black box. This is done so that I can use the connectors supplied (green wire going to the switch and red going to the AC accessories transformer).
4) Then I wire a DPDT relay to the wires that are labeled and color coded. Make sure you mark each side of the replaced switch and understand what is the common (center) wire.
Now with a relay you can use a DCC controlled relay module to control the switch.
I have left out a lot of detail as this would get very long so watch for an upcoming youtube video!