It would help greatly to have the codes the truck threw. Do you have any type of Scan gauge or other monitor on your truck? Seems strange your truck would lose power from a bad alternator. Did you hear your engine fan clutch come on while climbing the hill. My truck did something similar while pulling our fifth wheel up a hill, it turned out to be a bad fan clutch. Only did it while towing, no load no issue. You need a good engine monitor to tell you what is going on, I have the Scan Gauge II. Tells me the water temp, oil temp, granny temp and FICM voltage. If truck trips a code I can instantly see what is and reset the computer. Hope this helps.
