2010 Nissan Titan SE with 105k on the clock.

Bought it used from a Ford dealership who swore up and down that it was an older gentleman who had just traded it in after having a brand new transmission put in it and that the truck had no issues.
After putting 1,000 miles on it in the last few months since I bought it, I don't believe them one bit that its a brand new trans. The issue is that while I have a full powertrain warranty for 2 years on it, Obviously a ford mechanic won't know much about a Nissan and I'd much rather have a nissan mechanic take a look at it but I only have my warranty through THAT specific ford dealership I bought it from.

Here's the issue, I live in SW Florida where its VERY hot, and my commute is mostly stop light to stop light, with a fair amount of idling in traffic. I don't usually ever find myself on the interstate, and I drive the truck in "D" gear with albeit a fairly heavy foot, and the transmission regularly reaches the "H" on the trans temp gauge but comes down the faster I go. This is obviously a critical issue to have, and one that's not only annoying but basically means I can't drive the thing.

So my question to all of you that have had older Titans: Is transmission overheating really that normal and common as I have read about online with these trucks? Mine overheats anytime im not doing 85 on the freeway, cannot sit in traffic for ANY amount of time or else it WILL boil itself, and gets HOT after just 10 or 15 minutes of driving.

Help Please! Any Possible fixes or solutions?