our 02 has 100k on it and no problems with the tranny or motor
Be sure to do a compression check also.
Pull the dipstick and see what condition the oil is in, if it's jet black and reeks of hydrocarbons, run away, this is probably the norm for how the previous owner maintained the truck.
Open the radiator and shine a light in there. If it's full of mung, run away because the cooling system may not be in good order either.
PS. I'd LOVE to know how you guys are getting 20+ mpg in your 4.0L Explorer's. I have NEVER gotten better than 19 in mine.
I got to ask... whats "mung"?