Transmission cooler

I've got an 06 with the towing package with transmission cooler but assuming my Torque app was reading my temps correctly, I'm still running warmer than I'd like while towing my Jayco 23B. I weighed the trailer empty and it weighted 4025 and there is no way I had any more than 1000 lbs worth of stuff. Ambient temps were in the 80's. Coolant temp never reached 200. Transmission temp #1 (pan I believe) was running in the 220 and briefly peaked at 250 on a long straight incline. #2 (coil I believe) ran in the low 200's. In doing some research it looks like there are better, more efficient coolers out there.
http://www.transmissioncoolers.us/category/hayden-transaver-cooler.html
I was thinking about going with either the 1678 or 1679, both of which I've seen pics installed in Tacoma's in older threads. I found this site with a ton of choices but I couldn't really tell you what I'm looking for.
http://www.summitracing.com/search?keyword=transmission cooler
Is the larger cooler inherently better or are there other factors I need to take into account. Does anybody has any experience with these and if they saw a noticeable improvement? Anybody have any opinions on anything better out there? From my research it looks like the plate and fin type is better at cooling.

 

I run the

$51 Hayden 678 Universal Rapid-Cool 9.5” x 11” Add-On Transmission Cooler – Not for Direct Replacement of the OE Cooler

Hayden 678...works perfect...gains in going with the 679 would have been negligible, would require relocating horns and such

 

Ended up buying the B&M 70264 which is rated at 14,400 btu. Has anybody ran their auxillary cooler in series with the TRD one? I'm curious if I should replace it or just add the B&M to it.

 

You could do it...unnecessary, imo. There is also the possibility of overcooling the fluid to the point of being below optimal operating temp, which is between 150*-180*f. Any number of problems can result, such as hard shifts and others

My phone won't let me add a link for whatever reason....Google "overcool transmission" or bob is the oil guy has good info

 

This may be a dumb question but here it goes. My truck has 65k on it and the tranny fluid is good for 100k. In order to avoid a lot of money and hassle, is it possible to fill up the new cooler with tranny fluid after hooking up the hose to one side? I have no idea how much fluid it will take and I'll lose in the change so my simple mind thought this was a simple solution.

 

Possible...yes.

Recommended...no.

I'd go ahead and follow the procedure below, after you install the new cooler.


http://www.tacomaworld.com/forum/2nd-gen-tacomas/63851-how-drain-refill-automatic-transmission.html

This is what I did at 40k when I bought the truck...it didn't come with a hitch or the rest if the tow package...wanted it that way, I know the po never abused it towing

 

I forgot to add info to the other post...here goes...

Toyota revised the service interval from 100,000 mi to 60k on the automatic trans. You are there now. Might as well take the opportunity, while its open, to do a full service...I would. Cheap to do (realitively).