overheating in summer, no heat in winter

i have a 98 2 door with the 4.0....this past winter it would not get hot enough for decent heat, and now it overheats on trails and in traffic (A/C on or not) the only mods i have are a flex fan (no fan clutch), but i have no shrowd, because it wouldnt fit. Does the shrowd really do that much, or is something not working right? if so, what should i do?

The shroud really does make a big difference. When in place, it forces the fan to only pull air through the radiator, but without, it can pull it from all "around" it.

sounds like a stuck or bad thermostat. Change with a OEM replacement, and flush system.