Just an FYI before I get to the meat of this post. I reported this to rsc. Being I consider it minor, and I'm sure rsc also I just don't expect a fix anytime soon. Not a knock, just reality.
Anyway. The coach doesn't have bogie audio aliased or a child object for Wagon sounds. I added bogie audio myself and that works fine.
It is the Wagon audio child object which is making me scratch my head. I've changed and added Wagon audio to other stock numerous times but the p70 threw me a bone. The audio is playing, but it is just barely audible. I mean you really have to listen close to hear it. For example. I took the entire Amfleet Wagon audio entry and inserted it into the p70 blueprint. You can just barely hear it. Yet on Amfleet it is normal volume. I can't for the life of me figure out what is interrupting the playback volume of it once it is placed in the p70 blueprint.
Driving me nuts as I'm usually good at figuring these things out myself.