Towing with an auto tranny

Early model 1st gen specifically, but general advice welcome.

I have experience towing, but that doesn't mean I know what I'm doing, or that I'm doing things right. I towed a 17ft, 3,000lb camper trailer quite a bit every summer for the last ~8 years, with a 3.4L manual 5 speed Tacoma.

Now I have an '02 V8 auto Tundra. I'm still generally learning best practices for using an auto in mountain pass country. I towed my trailer for the first time last week, and was unsure how to approach steep mountain passes. Yes, I always tow with overdrive off. But on steep hills, I'm not sure whether or not to downshift. If I try to stay at a reasonable speed of about 60mph, the transmission shifts about every 10 seconds, back & forth. I heard that can overheat and damage it.

But then I read this in the owner's manual.



Well, what's a "long time"? It makes sense to me to avoid constant shifting. Putting it in "2" and holding rpm around 3,000 makes sense. But...which is going to cause overheating and damage? Long hauls in "L" or "2"? Or long hauls in "D" with the tranny constantly searching for gears?

Coming from a manual transmission, I definitely understand engine braking on the way downhill. And with the manual, I never thought about overheating the transmission. I'd climb hills in 4th, 45mph, 3,000rpm, flashers on. For however long it took.

If anyone has ideas, and general best practices for operating an auto tranny while towing (aside from the obvious O/D off), let me know!

 

The item you have to worry about that they are referring to is the torque converter lock up.
Your transmission probably only locks the torque converter in 3rd and 4th gears under certain circumstances.
In the low gears, the torque converter will not lock. Under that heavy load, high rpms and unlocked torque converter will cause the trans fluid temps to climb quickly. If your trans cooler and air across the cooler are not sufficient, it can overheat.
I’d recommend obtaining a real trans temp gauge to monitor the pan temps. Just the torque converter being unlocked isn’t an issue (vehicles didn’t have lock ups until the 80s, some until the 90s) as long as you can control it the heat generated.
But just shifting to drive doesn’t mean the trans will actually go into 3rd or lock the TC. Monitor temps.

 

Yes monitoring trans temps is Best. I use Torque Pro ($5 for android or apple) - it uses a standard 'elm327' type obdII blue tooth connector to display all the ECU info available.

As stated you're already doing the right thing to turn OD off when climbing and back on otherwise. I think your trans only has OD in its top gear so any below that are good to use climbing - lower gears will not increase engine or trans temps - it will help keep them down. Luck and enjoy that UR2.

 

Alright thanks. I recently bought a code reader and decided to go with a more traditional style, but I did considering getting the full real-time phone-app style. Probably should have. I agree, being able to see the transmission temp will take a lot of guess work out of it.

 

With how my transmission is geared, seems like shifting into 2 and keeping rpm around 3200-3500 treats my truck pretty well on mountain passes. That puts me at 50mph, which is good enough for me. And I don't have to feel my transmission shifting constantly.

Will still consider a temp monitor in the near future.