I have some Bachmann GP-40's in the Alaska line but not with sound. Since this is 50% Bachmann, I think it's OK to ask ... since Bachmann does not make a GP-40 with sound but does make a GP-40 in the Alaska line without sound, and I have found GP-40's with sound from Broadway Limited, but not in the Alaska line, has anyone tried to put a Bachmann GP-40 shell on a Broadway Limited DCC w/ Sound Chassis? Hoping since they are both GP-40's and most mfg's are fairly similar, it may be easier to do this than to adapt the Bachmann GP-40 chassis to include sound.
The easiest solution to this problem is either to repaint the Broadway Limited locomotive shell if you are good with paint and decals or to take a Bachmann locomotive with the Alaska shell and hardwire a microtsunami (or other small) sound decoder into the locomotive and select a small speaker and baffle. I have a Broadway Limited SD40 and a Bachmann SD40 and swapping the shells would require a great deal of modification to the interior components and the shells including milling and relocating of components.
Hopefully you are a good painter as that is the easiest solution for most modelers probably since they have a lot of experience painting and decaling models.
Discussed this with my local train store (H&R Trains, PInellas Park, FL) and Dave the train expert said the frames are not compatable even with a lot of work as they are different widths. I bought a very thin speaker and will try to mill out some of the metal frame under the fuel tank to hold the speaker. The speaker I got is about 1/16" of an inch thick and probably will not require much metal removal. Dave has a new sound board that will work also. Hopefully, this will convert the Bachman GP40 to sound.
Go to the search button and enter sound install bapguy user. Scroll down to adding sound to dcc. I think it's the 12 entry. I posted a photo of my sound install in my GP35. Since the top of the frames are similar this might work for you. I used a 1/2" speaker with an enclose. Joe