transmission or sensor?

well if anybody's seen the national weather they know it's been raining for like the last month here in texas, and i was thinking the gp was feeling left out so i took it out for a drive and had some studdering going down the street, i mean you could really feel it jerking kinda like when it's choking low on gas, but i had half a tank so i pulled over and checked my fluids and both were where they should be. i just changed the transmission fluid over a month ago and hadn't had any problems, and did the oil at the same time, both were clean as could be. i never paid any attention to it but i use mobile one oil and when i checked the oil it was dark and had a greenish tint on the rag where it was wiped, that normal? the studdering pretty much went away when i the temp hit 180, but after that you could feel it still very lightly only in first. so could it be a warming problem? there's only a couple hundred miles over 50k on the transmission and the car gets babied. my extended warranty ran out over 200 miles ago and i'ld hate it to be the transmission, hopefully someone's experienced this before and knows what it is.

Do you have dex cool coolant or the green anti-freeze? Also, what year and engine size do you have.

orange dex cool all the way, 01 gtp 3.8l 231ci

oh yeah one more thing, if i the cat needs to be replaced would it be a cause for this? before i found the problem with my car it ran for maybe a month, month and a half like that and ever so often it'll "fart" so maybe the cat bed could have been burnt or dirtied up. but then if that was the case wouldn't an o2 sensor be firing up a code?

Was wondering if you are leaking coolant into your oil from a leaking upper plenum intake coolant gasket. These 3.8 GP's are well known for this. If your oil doesn't look overfilled, then this may not be your problem.