I have an Athearn BB GP40-2 and 3 of the newer RTR Athearn GP38-2s with the crew frying headlights. I need to convert these to dcc and am wondering if anyone knows of a write up or wants to explain the best way to do this.
Depending on how new the RTR's are, they may be DCC ready. If not Digitrax makes a harness for easy installation into Athearn diesels that are not DCC ready. Their DH123AT and DH163AT decoders come with the "no solder" harnesses. If you already have the decoders with different harnesses, then all you will need to get are just the harnesses, the DHAT. These harnesses will fit many other decoders as well, not just Digitrax. Go here to read about them:
http://www.digitrax.com/menu_mobiledecoders.php
I have attempted to use the harness a few times. I have found it to be just as easy to solder the decoder in without it as the wires will often break off of the clips It is very easy to add LED's while your in there too. Miniatronics Surface Mount Yeloglo LEDs work well and they come with resistors in the pack. Remember heat shrink tubing is your friend when it comes to soldering the LED's to the decoder wires.
I'd run a jumper between the clips to get pickup from both trucks for sure.
I also run wires off the other side of the trucks instead of relying on the frame for pickup like in that example.