Question about Converting Atlas O 3 rail locomotive to 2 rail

Depending on what your end goals are, it might be less work to just sell your 3R trucks and wheels.  Instead, you could buy a complete selection of 2R drive parts- trucks, wheelsets, gearboxes, etc., from P&D Hobby Shop.  They should have Blomberg-style trucks in both brass and plastic (although they might not be identical to what was used on a GP60.)

I'm pretty sure the Weaver-style drive with a central motor and individual axle gearboxes will perform better than the stock China drive.  It can be geared lower, of that I'm sure.  Good luck with your project, whichever way you decide to go.

It might be better just to find a factory two-rail version. I did that with an ALCo RSD5/7.

Atlas shows the gp35 2-rail power trucks in stock.  If you look at the parts diagrams, I think you'll find that they are the same as the gp60 trucks.  The one exception is with the side frames, there is a snubber added to one axle of each truck on the gp60, which is why the gp60 trucks assemblies have a part  number that is distinct from the gp35 truck assembly.  But if you look at all of the component parts, gears, axles, bushings, etc, the part numbers are the same for each truck.  The side frame swap is a matter of removing two screws per side, the frame parts themselves all share the same mounting points.

One other caveat to keep in mind is that the Atlas parts inventory shown on their site does not always match what they actually have on hand.  So it would be a good idea to call the parts department and verify that parts are in stock.

Hope that helps,
Jim

Shapeways has both the pilot spacers and coupler pilot pockets for GP60's.I have used them and work perfect. "Gandyman and Son Trains" produced the parts.

Thanks for all of the info, everyone. Funny enough, I went to order the locomotive today, and it had been sold. I'll keep this info in mind when I'm looking at other locomotives though!

you absolutly have to changes the wheelsets and add pickups to the insulated side.

I have converted a pair of dummy C425 to 2 rail using the P&D drive.    It is not too difficult but it is not a drop in fit.    It is a totally different style drive.     The most complex is  you have to make new bolsters to mount the trucks, and  you have to mount the bolsters to the chassis.     these are up in frame and are not fancy, just a brass plate works which is what I did.    You have to drill a hole centered in the bolster to mount the truck.    I drilled and tapped my chassis bolsters for 2-56 screws and mounted the plates that way.     You have to build a motor mount too, but that is not hard.  

Converting with Atlas drop in 2-rail trucks would be mostly trivial, just wiring.    But  you do still have china drive.    Of all the china drives, I have found the atlas to be the smoothest.   I still like single motor drives better.