I feel like all the things you listed are exactly the reason auto transmissions get wrecked in off roaders.
Tall tires, big bumpers, loaded out truck and slow speed with higher revs all equates to hotter trans temps.
This can only get worse if you did not change gearing with the larger tires.
I would also suggest using 4-low more often.
This takes a considerable amount of strain off of the torque converter to help keep fluid temps in check.
I generally like to run the biggest trans cooler that I can fit with a thermostatically controlled fan.
The only real issue here is that, even if you try to pick out some cheaper parts, by the time you get all the necessary bits to make it all function the way it should it's still not that cheap.
What parts do you need?
Well here's a rundown on what I like to have:
Big trans cooler with fan
These units on ebay are of pretty good build quality for the money and come with a fan.
The price isn't bad either.
https://www.ebay.com/itm/30-Row-10A...256288&hash=item3d2ef59de5:g:3ycAAOSwnJtb4VQt
Temp controlled bypass
Ideally you don't want you trans fluid being cooled until it is at least up to operating temp.
This bypass does just that. It installs before the cooler and opens a loop bypassing the cooler until the fluid is at operating temp.
https://www.ebay.com/itm/Derale-Tra...714739&hash=item51efce848c:g:TdAAAOSwlMdc3C50
(you can usually find these a fair bit cheaper. this was just the first one I came across on ebay for reference)
Thermo switch for the fan
Obviously this controls at what temp the fan comes on.
These can be as cheap or as expensive as you are comfortable with.
Naturally some are more reliable than others.
They make adjustable ones and fixed temp units and there are various mounting arrangements.
I sprang for some pricier units housed in some -10 an fittings so I could eliminate a couple of clamped joints in my system.
Dual remote trans filters
I am of the opinion that the more fluid the better.
Why not ad a bunch of capacity with a couple of big remote mounted trans fluid filters.
More fluid takes longer to heat up and wear out.
Not to mention the obvious but you also get a substantial amount more filtering capability over the stock trans filter.
I like these units from Derale.
https://www.ebay.com/itm/Derale-Eng...037225&hash=item51d8f13b4c:g:j4cAAOSwrWRc3C5~
Pretty standard rubber line with good clamps
For cost reasons I just roll with some properly rated rubber line and oetiker clamps that take the special pliers to close up.
I make sure I get the 360 degree clamps for more consistent clamping
you could do AN stuff if you really wanted to but for the price of two or three AN fittings and the line you can have a butt load of clamps of various sizes, another butt load of some plain ol' pipe threaded, barbed fittings in various sizes and the pliers to clamp them.
I also like using relatively standard stuff for the fact that if something goes wrong somewhere in the system you can generally get the stuff you need at any parts store to get it fixed or bypass something in order to get home.
My only caution would be to keep your line runs as short as you can to avoid any serious pressure drop across the entire system.
I have never experienced any issues with this but it is theoretically possible so just keep it in mind.
Beyond all of that complication, running two oil coolers is also a good idea as has been mentioned.
I should also mention that maybe you should give the truck a good once over to verify that it is not another issue that might be causing the trans to overheat.
it could be something as simple as the oil coolers location.
Is it safe to assume that the engine is not getting too hot.
Maybe the rad fan is not working and, if the stock trans cooler is the loop inside the radiator type set up, it could be causing the trans to warm up.
Could be an actual issue with the trans.
Do you notice any other trans related issues on the street or on any other occasion?
Just my thoughts on the topic.
