I would look at

http://www.soundtraxx.com/dsd/tsunami/1000at.php

Now you may have to do a little milling on the frame but you should be able to get this decoder to fit.  It is the board type for Atlas models but I find that they will fil most narrow hood diesels.  Look at part # 828041 EMD 645. I have installed this decoder in a couple of Athearn BB kits and they work very well.  Finding room for your speaker will be the biggest issue.  I suggest making your own baffle and using a sugar cube speaker (use 2 speakers if you have the room for better low end sound)  But as I see it, this is a very doable installation.

Is this the newer version

Is this the newer version with DCC or the older DC version? The newer ones have a place in the fuel tank for a speaker. Soundtraxx decoder # 828041. From looking at the diagram, the keep alive cap might fit on the frame step at the rear. This may help.  Joe

30 seconds...

Dear MRHers,

Um,

http://www.soundtraxx.com/choose/step3.php?t=ho&s=Bachmann

(check the 6th entry from the bottom of the list).

Decoder and Speaker Part # reccomendations listed...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

PS Many decoders can be "made to work" in various locos
​(depends on how much "modification" one is comfy with doing to said loco),
,
a "loco-make/model-specfic" physical form-factor decoder
(let alone the associated speaker)
is the exception, not the rule.

Said another way, there are many more loco models and internal config variants on the market than there are sound-decoders available...

Just seems like a bit much

You need the decoder. And a speaker. And a speaker box. And wires. And then have to figure out how to fit it all in. Maybe I'll just buy a locomotive with the sound decoder already installed. Seems like it would be much cheaper and easier on the nerves.

Decoder

^{If you like the challenge, then go for it.}

^{I have used a Dremel with diamond cutting wheel and belt sander to modify frames.}

^{If cost is an issue, there are Bachmann locos, diesel and steam online at good prices online with sound. They have a sound value line, also.}

^{I have done Bachmann diesels. Two 44 tonners and a 70 tonner with sound install using LokSound Micros. Those do not come with sound anyway.}

^Rich

Sound decoder for Bachmann

Bachmann has GP40's with sound value decoders.  Model Train Stuff has some.  Joe

http://www.modeltrainstuff.com/GP40-GP40X-GP40-2-Locomotives-HO-Scale-s/1568.htm?searching=Y&sort=3&cat=1568&show=30&page=1&brand=Bachmann

GP40

At Micro Mark. My source.

http://www.micromark.com/SearchResult.aspx?deptIdFilter=0&searchPhrase=gp40

The Favorite Spot is also a good source for Bachmann products.

Rich

But not Milwaukee Road

I have the DCC on board Milwaukee Road but they don't make one with sound.

Take the fuel tank cover off

Take the fuel tank cover off to see if there is room for a speaker. If it's DCC on board, just replace the PC board with a decoder. Or buy one with sound swap bodies and sell the old one.   Joe