Tips on Buying Cars: Used Vehicle, tranny fluid, hi mike

Question
Hi Bud,
I will be buying a used Jeep 4WD through advertised internet listings within the next few weeks. I've been told not to buy one that's had the area around the oil pan, transmission, and rear seals cleaned,(person may be hiding leaks). I'd also run from unusual noises, discolored or extra slick or sticky oil, oil or excessive wetness in exhaust pipe, in addition to oil in the radiator water.
Is there a way to test drive the jeep to determine if the tranny is sticking or slipping, in case they have added something to the tranny fluid in an attempt to cover it up?
Also,if the 4WD option ever develops problems over time, will the jeep still operate normally in 2WD?

Thank you very much!

Best,
Mike Eidson

Answer
Hi Mike and thanks for the question.  First, you should always check with carfax or edmunds.com to find about previous problems.  Second, I would recommend you find a GOOD mechanic and pay him to evaluate the vehicle for you.  He could also answer your question about 2wd,4wd.  Best of luck with your new vehicle.  Bud