With my Ram, I will lock out 6th gear when the EGT's start to climb when pulling a 6% slope or greater. I will lock out the transmission as the EGT's reach 1100F or greater temp. I will then pull in 5th gear for the rest of the slope, but the truck transmission does not hunt at all. I will shifting back into 6th gear at the bottom of the slope. I am also in tow haul mode 100% of the time when towing any load with the exhaust brake on. I have driven this way ever since I purchased my 2008 Ram new in Nov 07.
2016 34RL CC; 2008 Ram Mega Cab 2500HD, 6.7L, 68RFE 6 speed, 4X4, Smarty S67, 100K+miles