I know this is an old post but I myself recently purchased the 4-8-4 Union Pacific model 53502 and wanted to add a DCC module (8 pin) with sound to the unit. I too called Bachmann for assistance and the customer service tech was helpful. However, I found that the instructions provided by Bachmann, both verbally and written, were not the best way for me to perform the installation. I do want to note that I accept no responsibility if you were to follow the experience I have to share. But, for me, it definitely worked best. Prior to attempting the install of the decoder, I would suggest that you reference the following document on the Bachmann website (www.bachmanntrains.com/home-usa/dwg/dwgs/89912.pdf). The document is helpful and will give you an idea of the breakdown of the tender. You will notice that to the bottom right of the document there is an insert with a diagram and instructions; however, the instructions are very vague and do not provide information that, during my install experience, I found to be good to know. The following is what I experienced and will be sharing regarding the installation of a DCC decoder with or without a speaker inside the tender of the the 4-8-4 Union Pacific model 53502.

Per the instructions provided by Bachmann, which was to use a screwdriver placed between the two cables exiting the front of the tender that attach to the loco, I found that it would require a wide slot-tip screwdriver and a risk of putting to much pressure pressing down which in turn could snap the bottom plastic tender platform.  After much thought, I decided to use a very thin jewelers screwdriver and gently lift the top center of the front of the tender with my fingers which allowed me to carefully slide the flat end of the jewelers screwdriver in between the top center front of the tender and the top of the tender front cover.  Once slightly inside the tender with the jewelers screwdriver I carefully and gently pried the tender front cover forward and the the tender cover came out from the tender body. Please keep in mind and do notice that there is on the bottom of the tender front cover a tip that is inserted into the bottom body of the tender which holds the tender front cover in place. This tip is shown in the diagram and is visible when you look at the bottom of the tender carriage just in front of the front truck assembly.

It is important to share that the Bachmann instructions say that after removing the front cover and screw (front screw), that you then pull out the metal plates with the main PC board. However, once I had the tender front cover off and I was able to examine the inside of the tender body, I did notice red and black wires were soldered to the main PC board and both wires attached on their respective end to a screw and nut for electrical pickup from the truck wheels.  I also noticed that there are also two additional wires (blue) that are soldered to the main PC board for the rear light on the tender.  It is imperative to note that the metal plate with the main PC board attached cannot be pulled out all the way as per Bachmann's instructions unless the two screws holding the main PC board are removed and the main PC board is separated from the metal plates.  If the main PC board is not separated from the metal plates then the metal plates could only be pulled out gently until the slack of the wires is taken up. This information that I am sharing is not noted in the "www.bachmanntrains.com/home-usa/dwg/dwgs/89912.pdf".

As for myself, since my intentions were to install a DCC decoder with a speaker I separated the DCC main PC board from the metal plate in order to install the speaker inside towards the rear of the tender body being careful not to damage any of the wiring and connection points. Especially the wires for the rear light on he tender.

Hopefully, I was able to be as clear and concise as possible in order to help others in the installation of a decoder in the 4-8-4 Union Pacific model 53502.

RailMan63, glad to hear that you are moving forward with adding sound to your On30 4-6-0. You would definitely enjoy the loco more with sound. As for what Trainman203 shared, I do agree with him. No doubt the MRC decoder with sound is not at the level of a SoundTraxx or TSC decoder with sound. Or as RailMan63 referenced, a TCS Wow V4 Sound unit. However, as I mentioned in my prior post, the MRC decoder with sound satisfied my needs for adding a sound unit to my On30 4-6-0 which for me added an extra level of enjoyment than just being able to control speed, directions and lights. As for adding a 21 pin unit to a unit with an 8 pin connector, there are drop in PCB boards that will convert from 8 to 21. But once gain, the MRC currently met my needs and it was a remove and replace unit. Plus now I do have an extra decoder that I removed from the On30 4-6-0 that I could use that will give me speed, direction and lighting control. RailMan63, if you are interested I could provide you with a picture of how I have the MRC decoder with speaker installed in my Bachmann #28805.

The information you provided is correct. However, Conrail acquired that loco through mergers. GP-40 #3084 was originally a New York Central loco. In it's current product line, Bachmann shows that as model 63529 which is a DCC ready loco. However, in the past Bachmann could have produced it under the Conrail railroad with it being either DCC ready or DCC on board. Then again, it could have been a DC loco and converted to DCC. I know that you mentioned that it was part of a set and that you saw it on eBay. If you would like to share the item number I would be able to assist you further. Sorry I couldn't be of further assistance.

I am glad you made your decision and that the post provided by the Forum members were helpful with you making your decision. As I mentioned in my post, I did not provide input in order to endorse the product I decided to use for my loco. I was just providing my input due to I myself owning the same product referenced in the post. But I do have to say that I do agree with Ton N regarding the range of the transmitter is best within 25 feet. But then who , as manufacturers of transmitters, doesn't over advertise the range of their product. Plus I am not looking to be running any locos on my layout from a distance 75 feet. However, as for the decoder being basic, I disagree. Plus it does allow main track programming. The Lenz is an excellent product. Which I could attest to being that I had lived in Deutschland for quite sometime. Plus as we all know, the Bachmann E-Z Command DCC systems are Lenz products. However, model railroad hobbyist all know that not all DCC controllers/systems are able to program on the main track every decoder on the market. IMHO, as for the three choices that you narrowed yourself down to, the SoundTraxx is the excellent choice. Now don't get me wrong. The Phoenix and Sierra are excellent choices as well. However; as for the Sierra, which was a SoundTraxx product, has been discontinued for quite sometime. Also, both the Sierra and the Phoenix were produced for the large scale market (G Scale). Which having experience with opening the tender in the Bachmann #28657 and installing a decoder with sound, would make it quite difficult to install such a large PCB board. I hope this information is helpful. From a person who really loves the hobby of model railroading who just recently joined the Forum because I did want to share my knowledge and experience with those who love the hobby as well. Wishing you well in your endeavor.

Glad to hear. As for the answer to your question, yes. The decoder has various types of synchronized chuff sounds. Visit the following link (https://www.modelrectifier.com/dccdecoders-s/112.htm) for additional information and be sure to review the instruction manual for additional information. A reason I did go with this one is for me it was low cost, plug-n-play (no soldering involved) and met my requirements for adding sound to my steam loco. As for me, I am satisfied for what I paid for. Plus the bonus of the remote operation is a plus. Especially for the children to operate the loco. However, please keep in mind that I am not endorsing the product and suggest that you do additional research on all the decoders out there and select which would be best solution and options for you. However, if you do move forward with the MRC decoder please feel free to continue to reach out for any additional information or assistance.

There are quite a few DCC On Board locomotives that are dual mode, DC and DCC, that do not require any reprogramming in order to run in DC mode. Bachmann DCC On Board locos come without needing to be reprogrammed. However, as jward stated, the owner could have reprogrammed the CV for DC only. Provide additional information regarding the loco you are looking to purchase, such as Bachmann model number if available or if not available, the loco type and road number since you already said it was a Conrail railroad loco would be helpful and the Forum may be able to assist you further. BTW, I do agree with Trainman203, beware and ensure you know what you are purchasing. Trust me, there are many on this forum who have learned from experience or just have a story to tell. Wishing you well DrummerEGConrail.

My pleasure providing assistance. Any 8 pin socket decoder with speaker will work. Or you could purchase an 8 pin socket decoder with sound and pair it with the speaker of your choice. Please do keep in mind the amount of room available within the tender. With that said, a SoundTraxx decoder is a good choice. As for myself, I added the following from MRC and I am pleased with my choice, 021501 LOCO GENIE UNIVERSAL STEAM (Heavy) SOUND TRANSMITTER & RECEIVER - HO SCALE. I chose this decoder because I already had a steam loco with this setup and am happy with it, it was plug-n-play and I do enjoy the option of running DC, DCC or through the remote without having to use my controllers (throttles). Do keep in mind that the speaker included is quite a the large side but I had no problem incorporating the 021501 in my Bachmann #28805. MRC also makes one that is light steam, 021500 LOCO GENIE UNIVERSAL STEAM (Light) SOUND TRANSMITTER & RECEIVER - HO SCALE. Light or heavy would be the users preference; however, I did want to match the decoder sounds according to the steam loco. I did pick mine up at an excellent price with shipping. Just be sure to google if interested in additional information on the MRC and where to purchase at a price well below MSRP. But please do keep in mine that I am not endorsing the product but just giving you my reasons for purchasing the one I did. However, I do enjoy my locos with SoundTraxx as-well-as other brand decoders installed.

Hello RailMan 63, I myself picked up from the same retailer the Bachmann #28657 Spectrum On30 Baldwin 4-6-0 Steam Loco - DCC on Board, Greenbrier & Big Run Lumber Company. I replaced the factory installed decoder with a heavy steam sound NMRA 8 pin decoder with speaker. To replace the decoder there is no un-soldering or soldering involved but just carefully prying from side-to-side the installed NMRA 8 pin decoder from the PCB board. Do keep in mind that the decoder is installed under the PCB board so you would have to loosen the two screws holding the PCB board to the tender body in order to remove the existing decoder body. I hope this helps and if I could be of further assistance please feel free let me know. Take care!