RCLX?

What does this stand for? I saw it about two weeks ago on EMD GP something or other. It was gray overall with red lettering on the side and might have had a red roof and nose.

I believe you mean RLCX, which is the reporting mark for Relco. They are based in Minooka, Illinois and their primary business is rebuilding locomotives. The locomotive you saw was most likely one of their B39-8's (ex LMX), which they now own and lease out to other railroads, primarily CSX.

Railcar Custom Leasing, LLC, uses the reporting marks, you mentioned, although I would also imagine that you probably did see RLCX which is more common, to see on a locomotive. Regards

i saw one of their SD40-2's in Framingham a few weeks ago, it was cool, i thought they were a unit rental company