Overdrive and towing

I know the manaul says to tow in 4th gear not over drive but I was reading another rv forum and people were getting better gas milage when doing flat highway driving in over drive instead of 4th. Just curious on your guys thoughts, it was a R-pod forum and in wasn't just tacomas it was other light wieght TV too. Also found what looks to be a great little trailer for our Tacos to pull its called a Takena by chalet, its light with what looks to be good build quality there are different models I'm looking at the 21"6' version 4800 gvr. I'm going to take a look at one when I go to visit the parents in Oregon.

 

Above 70 wpuld be good for overdrive in my opinion

 

I have used overdrive in several vehicles towing on flat ground, if and only if I could put it in overdrive and it would hold the gear. If it started shifting in and out of OD I would turn overdrive off.

 

I've never towed anything before so this is probably a stupid question, but what about towing in a manual transmission? Is it fine to tow in 6th gear, or should I stay in a lower gear? Is there a certain RPM that I shouldn't go below? What about max speed when towing? Is that dependent on the trailer?

 

Towing in 6th gear is fine, in fact it actually makes 6th somewhat useful. You basically just shift when you feel like it needs it, just like you normally would.

 

x2. Keep it in O/D if it'll hold the higher gear, once it starts hunting for gears throw it down to 4.

 

X3....Exactly....OD was not meant for towing..that is why it has the shut off button.....a few more $$ in fuel is way better then killing yor tranny

I have a V8 auto tundra and it always hunts for gears even with a 2200lb trailer...I just keep it in 4th...tranny cooler keeps it cool and way better then shifting up/down all the time

 

Even pulling a 5x10 w/ drop gate trailer my D gear seems like it's lugging in my auto. Dropping it down (using a scangaugeII) takes about 1.5 - 2MPG hit, but the engine load went from 80% - 85% to ~50%.

In my case it's not the weight, it's mainly just good old wind resistance. I've towed in both 4 and D, and while I can squeeze a few more MPGs in D, I feel like my tranny is really struggling to keep the speed. 4 is pretty worry free and I can feel a much more responsive throttle.

 

i just towed a 12' uhaul trailer with mine on 85 through ga, sc, nc, and into va.. and got absolutely terrible mileage. i felt like i was beating on the truck more with it in 4 versus D.. and that i was getting much worse gas mileage in 4.. i think i averaged with a full load just over 12mpg.. but at my worst got 10.8 through a particularly hilly section between charlotte nc and ga

 

I feel safety and not overworking your tow vehicle (esp. the tranny) should be your concerns when towing....not mileage....IMO

 

I towed a 6x12 Uhaul cargo trailer this weekend and it towed pretty well in D all in all, but started hunting in hills so I went to 4 after that till I hit flats again.

Trailer was ~ 2000 unloaded and I had about 1000 # in it, so only about 3000#, which is a mid sized pull for me.

My travel trailer is right about 4100# and if I leave it in "D", it simply never shifts out of 4th, so that tells me it doesn't want to do OD for that much load.

But all in all, when pulling something like a 6x12 or my TT, if you're getting 10 + MPGs you're doing good.

 

I took my first try at towing a TT last week. I have two questions.

Driving 65 on flat ground, in 4 it ran about 2700 rpm. In D, it alternated between 2000 and 2300 rpm. It would switch once or twice a minute. Is that too much shifting? Driving in traffic without a trailer would shift more than that.

My other question is what is it shifting between? This is a 5 speed transmission, how does it have two gears above 4?

This is a 2011 SR5 with the V6 and the tow package.

 

2000 RPM is OverDrive, and 2300 is OD with the Torque Converter unlocked.

2700 RPM is 4th gear @ 65 MPG @ 3.73 rear axle.

Shifting 2x a minute makes me on the nervous side, but likely not too bad. Everytime your Torque Converter chooses to shift it generates heat.

To answer your next question, running 2700 RPM long term isn't bad and might net you the same if not better fuel mileage, will put less engine load on the truck and give you more throttle response if you need to move a little.

Don't expect better than 10 - 11 MPG no matter what gear, so just worry about keeping the truck working as easily as it can.

 

i actually just went through a school and learned about torque drive versus direct drive or lock out as we call it. i was really surprised to see it in my tacoma (going from 2300-2000 and back) since the school i went to was for maintenance of an assault amphibious vehicle with a 903 cummins and the craziest transmission i have ever seen. that being said... im glad im not the only one getting 11mpg haha.

and i would love an od off button instead of just shifting into 4th even though its the same thing (right?). for some reason it just feels right to have an od off or tow switch haha

 

I agree with you Transplant, the Tow mode button on the Tundras essentially handles it for you so you just put it in drive and get after it.

But yea, I manually select 4th so there's no question.

 

The reason you don't want to tow in OD is because when the tranny shifts it builds heat and when you build heat in the fluid it breaks down and then when the fluid breaks down the hard parts in the transmission suffer and die. If you can tow in OD and not have it hunt in and out of lock up and/or 4th then there's no reason I see to not do it. Ideally you would run a transmission temperature gauge and you could see exactly how hot the transmission is or isn't getting and make a judgement based on that. I want a temp gauge but for now I go by the shifting. Typically it'll hold OD with an empty utility trailer and with a load I will pull in 4th.

 

i was mainly going off the fact that i never saw the warning light for the trans ot haha. i would prefer a guage, but i dont tow enough for that mess.
i am downshifting rougher now though. downhill light braking it shifts down hard.

does going in and out of lockup a lot rough up the trans?

 

Yes and No. Like fvtalon said, it's more about heating up the transmission fluid to an unsafe level when it breaks down and fails to keep the transmission cool. Any shifting or unlocking will heat it up, further risking that.

That said, I think that temperature is like 250 F, and your transmission light will come on around 220 F and warn you.

There's currently not a way to monitor this temp in our trucks, a major disappointment for most of us towing peoples.

But the bottom line is this:
Heat up tranny fluid = breakdown of transmission sooner over time = lower life expectancy of truck.

Keeping it from shifting alot just makes the tranny last longer.

 

or just change the fluid more often??