Diagnosis Questions
Lorlando: First do you have gauges added to your truck yet? A fuel pressure gauge, EGT and boost gauge would be a minimum for your truck.
When you said your temperature kept going up, how far is up? The center of the temp gauge is 190* or so, and going above the center mark when towing 8000# during that heat wave and climbing 3-6% grades would not be unexpected. As long as the needle doesn't hit the top of the center range, you should be ok.
What would be unexpected is if the fan clutch on the fan didn't kick in, [and make a lot of noise] and cool down the temps back to near the center mark.
The ability of the radiator to get rid of heat is the result of the difference between the radiator temp and the air temp, so if the water temp rises some after a full throttle climb up a hill, the fan kicks in, and then the temp drops back to normal, all this is correct and normal.
If you don't have an egt gauge, and are a stick shift, you may have been lugging the engine down to the point that the egt's were way up there [this can happen on a totaly stock truck] this could be part of the problem. You should climb hills at around 2000-2200 rpm minimum or else you will create high EGTs at full throttle.
So: fill in your signature so we know what your truck is equiped with, tell us how you were towing [what gear or range, speed, headwind etc. ] and maybe we can help.
By the way, all the previous advice is good, and I would recommend using an Edge EZ or equivalent box with the boost elbow installed for towing. These basic timing and fuel boxes make the truck run like it should! With the boost elbow installed, the EGT's will be lower than stock with more power.
Give us some more info, and then we may be able to help. To fill in your signature, click the [user cp] button at the top of the page, then the [edit profile] button, and type away!
Greg L The Noise Nazi