Geof says:

Peter,

I don’t think changing your wheel sets is going to help very much in regards to the dirty wheel problem. The wheels are picking up the dirt from the track so switching to a less ‘dirt prone’ type of wheel doesn’t really solve anything since the dirt is still there in one form or another. Perhaps what you are using to clean your track is the real culprit if it leaves a sticky residue behind. I use Goo Be Gone (a label removing cleaning solution) on a felt pad track cleaning car pushed by the engine around the layout once a week. The standard ink eraser track cleaner also works well though its a bit more work intensive and hard to use on out of reach or hidden track areas.
I recently read an article where some people use a small amount of automobile automatic transmission fluid (!) (see Model Railroader May 2011 issue) that apparently lays down a light coating on the track which seems to increase track conductivity even THROUGH any track dirt. I have yet to try out this method myself but the article’s results are convincing.

The noisy diesel might be just something you’ll have to live with although you may want to check out the gear train for burrs or irregularities. I read where someone had a similar noise problem and they found the gear castings weren’t very ‘clean’ so they CAREFULLY filed off the burrs between the teeth and off the gear face(s) that they could find and the noise level was reduced considerably. That person’s engine also ran much smoother afterward so if you have jerky operation with that particular Athearn engine, a gear ‘tune-up’ may solve your problem.

Get back to me if any of this works. I’d be interested to know.

Hope this helps,

Geof from the US