I reckon the OP is MIA for now. It's my guess what he's experiencing is the high temps our auto trans can hit when climbing steep sustained grades. Even if you turn Overdrive off and you have an additional external trans cooler, the transmission temps can go through the roof on slow speed steep grades.
On 4wd trip with [MENTION=148218]JZiggy[/MENTION] off the California Coast near Big Sur, I learned that having your transfer case in 4Lo as opposed to 4HI can make a huge difference in your trans temp. When I was running in 4HI, my trans temp quickly climbed on the steep sustained fire roads we were on. After I stopped for a second time to let my trans cool down a bit, my buddy Jordan asked me if I was in 4hi or 4lo. When I said 4hi, he suggested I try 4lo and it was like night and day. If I would have kept driving in 4hi, I have no doubt I would have gotten the trans temp idiot light on my dash to light up because I was able to get it up to 230 degrees pretty quickly and we had a ton of more climbing to do. Once I shifted to 4lo, my trans temp never got above 170 degrees.
Now, if you're climbing steep and sustained paved grades, you can't exactly put your transfer case in 4lo because you would risk destroying your front differential and/or your CV axles. The best thing you can do in this situation is first be monitoring your trans temp and know when it's time to pull off for a little while and allow your trans temp to drop down a bit before continuing. If you had manual hubs, you do have the option to switch your transfer case into 4lo and have the front hubs unlocked so you could benefit from the lower gearing but avoid damaging your differential and/or CV axles.
