Overheating... STILL

[Tenny]

Alright, so ever since I bought my jeep a few years ago, my cooling system has always been a nightmare.

Things I have replaced:
-Radiator (4 times). Aluminum one in there now
-Thermostat / Thermostat Housing (High Flow From TurboCity, 180*f)
-Water pump - OEM
-Radiator Hoses - OEM
-Flushed the system multiple times
-Hood is lifted in the rear for a little bit of vent (not much)
-Mechanical fan clutch replaced with a new one
-Electrical fan is wired in via switch (also starts up fine w/o the switch)


It only happens when I leave the area and go camping. I wouldn't say it's dependent on altitude, but it could be. This past trip it seemed that if the Jeep was running over 2k rpm, that it couldn't keep it cool. It never got into the Red, but it got pretty close and I pulled over to let it cool down. It does this mostly at highway speeds, never even gets close while off-roading.

At one point it started smoking a lot, and it was transmission fluid, let it cool down for about 15 minutes then went on, and never had that problem again.

So I am trying to figure it out what is wrong with it. The only thing I can think of is maybe the thermostat is stuck partially open / closed? My friend thinks it may be the head gasket, but that's only a guess on his part. So I am thinking about replacing the thermostat and putting some vents on the hood and going camping again and see if that helps at all.

I have checked the oil before, but never noticed anything wrong with the oil (like there was anti-freeze in it), so that's why I doubt it's the head gasket, is there anyway to know for sure it isn't? He made it sound like the headgasket is compressed too much and is possibly causing detonation...

Oh and the jeep has 170k miles, 33" tires 4.10 gears...