Looking at trying to keep the trans alive as long as possible and have been debating either a larger aluminum pan with cooling fins or one of those B & M external coolers with built in fan. I have a 2500 that always carries about 1200 pounds of stuff. Most of my driving is around town and in LA traffic. Ocasionally tow a trailer witha 5000 pound Jeep. Temp does not get above 185 but would like to keep it working as long as possible.
thanks guys

Never saw much of a drop with a pan, but did see a substantial drop with Mike L's cooler. 20 degree drop once installed.

I am running a TCI 278010 with synthetic fluid. I dropped maybe 10 degrees. Then I put on a B&M 70274 and it runs very cool. But then again I do not see as much traffic as most of you.

If your temp doesn't go over 185*, what are you worried about? I would just service regularly w/ a good quality synthetic. 185 is no where near hot.

Dont they already have an external cooler on them?

Yes all dmax vans come with a external trans cooler.

I'd say skip any additions. If the transmission is hunting, put it in tow haul mode. Otherwise change the fluid as recommended and you'll be fine.

thanks for all the input,will just change fluid and keep it the way GMC designed it.

keep it the way GMC designed it.
stop talking nonsense:D Statements like that could get you banned!

To funny, ya GM is a not a vendor on here so you better watch what you post.