Larry -
30 km/hr is about 20 mph. That is really slow!
Kwantau -
If your rig is 3462 lbs all loaded up, that is pretty light, which would have helped. I bet Larry was well over 4000 pounds.
As you made the crossing, how low did your road speed drop?
The reason I ask is that my own personal experience - far from professional - says that it is better to keep road speed up as much as you can while climbing a steep grade. My "testing ground" was repeated climbs of the Mogollon Rim in Arizona, usually on rte 260 from Payson to Strawberry or Payson to Heber. Many miles of constant 6-8% grade. In our 4.6-L Explorers, heavily loaded, if we slowed down "ease the load on the engine", tranny temp would rise into the danger zone. But if we downshifted and kept road speed to 40-50 mph or more, temp stayed reasonable. Not low, but reasonable. With no further knowledge, I conclude that the higher speed kept more cooling air flowing through the radiators, including the all-important auxiliary tranny cooler. (Larry, do you have one?) At 20 mph, there is virtually no cooling air beyond what the radiator fan can stir up. And since the air is thin at altitude, it cools even less.
I know it is counter-intuitive. Take it for what it is worth.
Bill
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