Here in the west, I try to stay around 50 in 5th. My truck has 3.92 gears, and 265x70 - 17's for tires. I also go down the hills at this same level. Being a tongue trailer puller, used to pull a 5th wheel, I like to move with the largest vehicles.
Getting pushed by passing traffic, sway control - equalizers in use, is something I'm used to. The mountains add a plus to the experience. I have to keep my wife happy, by smooth progress.
So far the dealers say 260's is not abnormal for this combination? Early on, it was a hot climb, I did see 270's. I slowed down and it got hotter to 274. Interstate - 5 in the, not so high, mountains of northern California and southern Oregon, can be a hot wind driven place. Like I posted, pages back, I had a tail wind on a steep grade. The air temperature dropped 20 degrees when I went over the Ashland summit. All was good.
I have made that trip two more times going both directions. I have traveled the route in the morning hours when air temperatures are in the 40's. The truck still gets into the 250's on engine oil. Everything else seems liveable.
Water gets hot but not too hot. Transmission is warm but cooler than water.
Seems to me "ZF" required a trans cooler, good for them.
If you need a test of your equipment. Interstate 5 north from Redding Ca. to Ashland, Ore. The wind blows, sometimes south to north, sometimes the other way. It is always a test. It is not high altitude, just a bunch of steep 2000 to high 3000 foot bursts. Ashland summit is only 4,400 feet but I say again steep.
Must not be a test path for vehicle analysis. I have seen Chrsler products on Interstate 70 in Colorado, never "I - 5".
