[MASTERBrian]

To add to this...

I have been doing some light reading on the subject. It does seem that the pump, pumps at speed of engine, so if higher rpms of 1st gear, it would go with my thought of pumping fluid faster through cooler, which accounts for lower temps.

I honestly don't recall if I downshifted any going up, but maybe I should have. I was trying various things the last 2 miles, when temps hit the 200 mark, to see what worked. Anything much above 205-210, was only the last few minutes to get to the turn around point, so not worried about damage and like I said I was sure to stay below 220.

I'll admit I don't do lots of steep driving. I've towed boats and other trailers through hills and lower elevation mountains and im fully aware to downshift if vehicle is constantly shifting, but on this drive it wasn't doing that. That said, if it's correct that the pump spins faster with higher rpms, then it'd make sense that downshifting to get rpms up would be the way to go. The question here is what gear would you choose? ..... or would you just keep the rpms up, while maintaining the speed wanted, to keep the fluid moving faster?

It's also been several years since I drove to the peak, in my other suburbans, and it's very possible as I've gone higher I had shifted to lower gear to make the climb, thus avoiding overheating transmission without thinking about it. Again, no gauge on those. I'd say to mile 10, 35mph+ isn't out of question at times.... it really depends on traffic and taking on the views.