Change to synthetic automatic transmission fluid for towing?

[Catchlight]

I'm about to start towing a 21' travel trailer with my 2011 Trail Edition. The trailer's weight, wet and fully loaded, is 4300 pounds, fairly close to the 4Runner's rated towing capacity of 5000 pounds.

Here in Canada (and maybe everywhere) 4Runners come with a factory transmission cooler, but am not sure how effective it is compared to aftermarket AT coolers.

For towing on steep highway grades during hot summer weather I'm wondering if synthetic automatic transmission fluid would reduce heat buildup, last longer, and be worth the extra cost.

For the record, I will not use 5th gear when towing, and will shift manually to prevent the AT from searching for the "right" gear.

I'd be interested to know how the AT temperature situation was for anyone who has towed close to 5000 pounds in the summer using either conventional or synthetic AT fluid. Thanks!

 

[1engineer]

Read this + the link inside from Quentin http://www.toyota-4runner.org/5th-gen-t4rs/119248-trans-temp-hit-208-degrees-today.html

 

[N2GLOCK]

I towed my 19' jet boat and all of our gear across the Mojave desert last year. When I arrived in Needles it was 118 F The whole 5 days I towed the boat back and forth from the hotel to Lake Mohave in AZ and getting to the lake involved some climbing. The entire trip it was between 112 F and 120 F I did not have a scangauge at the time as I do now so I don't know what temp the trans fluid reached. All I know is that the trans. temp warning lamp didn't turn on. Honestly I was kinda nervous about towing in that heat w/ the 4R since it lacks an auxilary cooler. The times I've done that same exact trip were with a Dodge truck and a Tacoma both of which I previously owned and both had external trans. coolers.

 

[N2GLOCK]

And somebody correct me if I'm wrong here....but don't our 4R's come w/ synthetic ATF from the factory?

 

[JeremyB]

I towed my 19' jet boat and all of our gear across the Mojave desert last year. When I arrived in Needles it was 118 F The whole 5 days I towed the boat back and forth from the hotel to Lake Mohave in AZ and getting to the lake involved some climbing. The entire trip it was between 112 F and 120 F I did not have a scangauge at the time as I do now so I don't know what temp the trans fluid reached. All I know is that the trans. temp warning lamp didn't turn on. Honestly I was kinda nervous about towing in that heat w/ the 4R since it lacks an auxilary cooler. The times I've done that same exact trip were with a Dodge truck and a Tacoma both of which I previously owned and both had external trans. coolers.

I you believe this guy, the trans temp warning light comes on at a very high value - 302 degrees. Unsure if that is the converter sensor or the pan sensor. So a lack of tranny light doesn't necessarily mean everything is hunky dory.

And somebody correct me if I'm wrong here....but don't our 4R's come w/ synthetic ATF from the factory?

The Googles says it is synthetic/semi-synthetic. Toyota is quite proud of its low viscosity at low temperatures compared to the previous generation tranny fluid, which helps fuel economy.
Interesting Toyota WS ATF Research. | ATF, Differential, Trans, Brakes, P/S | Bob Is The Oil Guy
Toyota WS...my eyes hurt from reading | ATF, Differential, Trans, Brakes, P/S | Bob Is The Oil Guy

It's complicated?

 

[Catchlight]

Thanks for the links

Useful info on monitoring and controlling AT temperature in both of those links, 1Engineer. Thanks.

None of those posters mention first-hand experience with synthetic AT fluid, though. Surely someone has made the switch.