I have a 2005 Nissan Titan kingcab (auto with big tow package) with a tow rating of 9500 lb. I tow a 2006 Featherlite 2 horse bumper pull trailer with an empty weight of approx. 3,000 lbs. Last season I drove the trailer with our two horses (approx 1900 lbs total)plus 500 lbs of extras (hay, feed,cooler,etc). Two adults in the truck(approximately 360 lbs total). I noticed when I was driving up fairly steep long hills the transmission temp. gauge was on the borderline of going into the hot range. It never actually went into the red zone but definitely caused concern. Then when we would level out it would slowly go back to normal. I should note that I had the tow button on. Read on a Titan forum site others have had this issue. They recommend shifting to 3rd or 4th gear for the hills or even just towing in 3rd all the time. Others said a larger or additional transmission cooler would help alot. What do you think of these two options?

Kellym .. Welcome to the forum.

Either of the options you're considering will help. To choose which way to go... Consider why the transmission is heating on a long hard pull. The torque converter takes the place of a clutch in a manual transmission truck. The TC is a fluid coupling. Meaning that it has two turbine wheels facing each other (simplified). One is driven by the engine, the other is connected eventually to the wheels. The driven turbine wheel spins and drags the other wheel around with the fluid. As the wheels spin together, there is a bit of slip between them. This slip creates heat in the fluid. If there is a lot of weight holding the wheels (as a loaded trailer) there will be more slip. More slip equals more heat.

You either have to cool the fluid (using a cooler) or reduce the force the weight applies (lower gear).

Using a lower gear uses more fuel as the engine has to spin more times to go the distance. The fluid cooler is aways a drag on fluid circulation.

Since your transmission just heats within the design limits, I'd get another cooler installed. And maintain the transmission on the severe service schedule.

Then if you are pulling a greater load or steeper hill than usual, select a lower gear for the climb.

Thank you for your quick response and the great information. I contacted a transmission shop after doing a search for a reputable company on the BBB site. The transmission cooler will cost $169. installed, well worth the cost! Will post how it does after installation.