oil in my radiator Reservoir

[Hammerhead]

If you have a liquid cooled transmission, then I would suggest you pull oil samples of both your engine as well as the transmission and have them tested. Specifically telling the lab you are looking for coolant intrusion. If you can scrape a decent amount of the oil emulsion from the rad tank, send some of that along as well to confirm which type of oil it is.
The hell you say Hammer!
I know, if I hadn't had it happen to me, I'd be really skeptical as well. A couple years back I had some oil show up in my rad as well. For some reason it didn't appear as engine oil, my inframe was just under a year old, and I just thought it was odd. I pulled samples from the engine oil, tranny (liquid cooled), and my APU (cause it's tied into the coolant system too), and scraped a bunch of the emulsion from the rad. Low and behold, it was transmission oil. The tranny sample came back with such small traces of coolant, that if I hadn't specified what I was looking for, it may have been overlooked, they tested it three times to confirm. When the emulsion was analyzed, there was one additive quantity that only matched the tranny. The lab emailed the results & called me to verify, transmission. I would have never thought the transmission being as low as it is, not pressurized that it could actually force oil into the coolant side of the tranny cooler, but it did.