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Slow down and spend more time in 4th.
I pulled our 32' camper out to the Grand Tetons and Yellowstone last summer behind our 2012 XL Denali with the 6.2 from Virginia. I've made some mods to it including a bigger cam, 2-row Cold Case radiator and a Derale fan-forced transmission cooler and had no problems, but I would have been fine without those mods and the factory setup. Lots of folks pulling campers this size behind their 5.3 and having good results.
That’s climbing up still in tow haul mode correct? If so,does that effect engine braking on the way down since you’re now in the M drive?
Thank you ,this is great information and I’m trying to figure out when to put it in one of those gears and take it out.
When I tow, I use tow/haul mode and then set the transmission to M5 to keep it from hunting in and out of 6th. If I'm pulling into a headwind and it's hunting between 4/5 then I'll put it in M4 until I think it'll hold 5th again. The main thing is to prevent it from hunting/shifting frequently in whatever the current conditions are.
Do you keep it in one of those gears even when going downhill? The reason why I ask is because I was told that the engine braking is disengaged when it’s in one of those gears.
The manual mode on these trucks works differently than in other vehicles, so I think that confuses people. In other vehicles, when you use manual mode and select a gear, it effectively locks the transmission into that gear. In these trucks, manual mode actually selects a range of gears, up to and including the number shown in the gear selector display. So when you select M4, the truck will choose whichever gear the computer thinks it needs, up to but not above, 4th gear. When you use tow/haul mode, it will also use engine braking and may even drop down into a lower gear on its own. You can also use the selector buttons on the descent when in manual mode to select a lower maximum gear to ensure better engine braking. Using this technique, I have had no problems descending 8-9% grades with the camper behind me, and not needing to use the brakes much, keeping them cool and ready should I need to make a sudden stop.
^^^ This. There are YouTube videos for how to do this. The 'pill' is a thermostat that prevents the transmission fluid from flowing through the external cooler circuit until it reaches something like 195ºF. That's a problem when towing heavy because by the time the fluid heats up enough to start flowing through the cooler, you're well on your way to a fluid temperature spike. When you 'flip the pill', it allows the fluid to flow through the cooler circuit beginning at a much lower temperature, preventing thermal runaway and temperature spikes.
