I would suggest lubing and oiling the trucks and the motor(s) if you can. I usually only hear a growl when Itry to send a steamer around too tight of a curve.

 

Well, I did oil the trucks- that was my first move. I'm not quite sure where to oil the motor, though. I'll open it up again and look. Not sure if my make shift kitchen table layout has too much of a curve- 4 10" to make a tight oval. Maybe this is too much for this diesel?
This is temporary of course until I build my table. I think this is motor related because if I grab the engine and try to hold it back, I hear the same growling noise, like the motor is straining. It's not loud, mind you- the hollow plastic body seems to resonate with this noise. This is the first diesel of the 1970's "one sided traction tire" type I ever owned, so I'm really not familiar with it. My new Sante Fe Lion Chief of course does NOT exhibit the same growling noise, but that has twin motors, and FOUR traction tires. And, of course my 2036 and 2037 steamers take those turns with no complaint.

 

It could also be the wheel spacing. If they are not properly spaced they will bind on the rails.

 

Remember, this is a Pulmore motor, they do have a growl when they run, more so under load.

 

Well, one thing did work- I oriented the engine so that it PULLS- the cab is in the front with the big "E" facing outward.
The motor is also under the cab. If that's the way it's SUPPOSED to be, I'm going to feel pretty foolish. At any rate, no more "growling" under load. Sorry I wasted anyone's time!

 

Railroads ran them either way, it depended on the RR and the specific circumstances. In the case of a single engine Pulmore motored locomotive, having the motor in the rear will give you lots more pulling power as a rule. As you can see, they ran them either way.

 

I figured that in the real world. I'm still fooling around with the "resonant howling" issue, and here's what I've discovered. I carefully bent the metal railings away from the body so they are still in the recess, but not really contacting the body, based on my suspicion that the hollow plastic body really exaggerates the noise. Then, I slightly loosened the two phillips head screws. That seemed to quiet it down. I guess I'm not used to hearing that noise, as my only prior experience has been the 2036 and 2037. I'm just re entering the hobby. Thanks for all the tips. So glad I found this forum!