Replacement for transmission cooler

I've read that the transmission cooler that comes with the 4.0 tow package is not really up to heavy duty usage. After my last camping trip I believe that may be the case, and I'm thinking hard about replacing it.

I have an 'O6 Prerunner that I tow a 3500 TT with in generally tough conditions (lotsa passes and foothills). I bought a Scangauge a couple months ago specifically to monitor my transmission temperature. We got some 50 degree days and took a couple hundred mile trip that's one of my easier pulls. Well, I was a little concerned with how easily the trans temp gauge went above the 225 degree area-both climbing and in traffic.

Has anyone replaced their stock cooler with a Hayden, Derale, or other brand stacked plate type, what size/model, and how satisfied are you with it?

Incidently, the fluid has been recently exchanged with Toyota WS, and I never tow in drive, so old fluid and excessive shifting aren't part of my problem. It's just that if I'm getting this type of heat now, what's it gonna be with summer temperatures and tougher pulls?

 

I didn't have the tow package to begin with, but I installed a Hayden on mine. I think it was a 678, many people here have used them.

I don't tow yet, but worst I think I've seen mine is maybe 185 with the box loaded down with stuff climbing through windy steep hills in back woods at 30-45MPH.

I had the Hayden running after the radiator cooler, but it ran too cold (around 105 all the time), so I put it before the radiator and it runs about 145 in the summer empty.