Tow haul mode

[Tequila]

I am sure this has been discussed before, but who uses it and how? I have a 1 ton diesel dually and will be towing a 5500 lb (dry) trailer. I am assuming it will lower fuel economy? Am I correct in assumign i shoudl probably turn it off on relative flat terrain and engage it in hilly terrain. So far I have tended to use it only for goign down steep grades so it downshifts when I brake.

[MitchF150]

T/H mode keeps your trans in a lower gear longer, yes... But that's because it's not UNLOCKING the torque converter which will generate a TON of heat in the fluid in a matter of MINUTES... 😉

So, if you like the fact that you are running in a higher gear, but in an UNLOCKED TC condition, you obviously don't pay attention to your trans temps... 😉

I'd rather run higher rpms in a LOCKED TC condition than a lower rpm UNLOCKED and generating a TON of heat in my trans.... 🙂

That's just me, so do as you feel works best for you.. 😉

Mitch

[Slownsy]

It can case more damage to engine if using to high a gear than to use more revs and lover gear if gearbox starts hunting definitely lock in lover gear.
Frank.

[shepcal]

S.R.Joe- my Allison is 100 times better than any tranny your pappy used. I'm not hurting it one bit.
I went from 2.45's to 2.65's on my 07 Chevy Duramax and have found I get better mileage even when not towing in T/H

Just say'n, Shep

[Bigbird65]

Anytime my trailer is hooked up the transmission is in the tow/haul mode. The Pentastar V6 really pulls my TT well. I limit the upper gear to 6. It rarely shifts at highway speed unless I'm going up a long hill.

[Skid_Row_Joe]

EcoBullet wrote:

Skid Row Joe wrote:
do not use that button to downshift the rig to brake it's speed. Use the foot brake, by a push and release methods so as not to burn up the brakes with a constant push on them. The transmission will wear adversely if you try using it as a braking device, especially on those long, steep grades.

I'm no expert, but this is just about backwards of what I've always read, and done myself. I think I've even read in an owner's manual or two that you should downshift when descending hills to allow the engine to brake, rather than overusing your brakes. If you go down much of a hill and don't use any sort of engine braking, you stand a good chance of brake failure due to overheating, even if you do push and release. Your method might work in Texas, but please don't try that in the mountains of Colorado.

With a trans overhaul or replacement that runs $3,000+ and a brake job running a few hundred - the math is easy on which system to brake with.

Anywhere, in the United States auto transmission downshifting will potentially harm the transmission. My Ford PSD's owners manual specifically states not using it as a braking device. If your method works for you have at it, but it does your trans. no good - whether you realize it or not is the only difference here. That includes Colorado, btw.:W

[kaydeejay]

johndeerefarmer wrote:
Tow/haul holds each gear longer so you should use more fuel. In other words instead of shifting into 6th at 1800rpm it might do it at 2000rpm. Th higher the rpm, the more fuel is used. I leave it off unless the truck is frequently hunting gears or if I need it for engine braking.

Not necessarily true - if the engine is not laboring and is producing the same power, the fuel usage will be the same.
In addition, the torque converter clutch locks up in the lower gears to save transmission oil temps. If there is less heat going into the trans fluid, then there may be a tad less fuel being used.
I have not noticed any fuel economy difference using T/H but I sure like the engine braking.

[captnjack]

My TV is a 2002 Suburban 2500 with 8.1 L engine. My owner's manual says to use T/H only when towing at 75% or more of GCWR. On a previous trip I used it even though I was below that weight. Engine was winding out a bit in all gears including top. It didn't just change the shift point. Gas mileage came out to about 7 3/4 MPG. Then I looked at manual and saw the recommendation. Most recent trip I didn't use it (and didn't miss it). MPG was around 11. Obviously a huge difference. No noticeable difference in tranny temp. In the future I'll only use it in steep mountains if necessary. I tow about 6000 lbs.

[BB_TX]

As noted the tow/haul alters the shift points to reduce "hunting" and also to keep the rpms up before it shifts to prevent lugging.
On mine I turn on tow/haul as soon as I hook up and it stays on until I unhook. But that is with a 35' 5er. With your lighter trailer and the dually it probably will not make much, if any, difference in your towing.

[johndeerefarmer]

KD4UPL wrote:
I don't understand all the reluctance to use a feature like T/H. It's there specifically to help the vehicle perform better under towing conditions. Why try and second guess the engineers and the manufacturer.
There's no logical reason that using T/H would lower your fuel mileage. It doesn't change your weight, wind resistance, vehicle speed, or gear ration. It just changes how the trans. shifts. Even if that did lower your mileage something like .01% it would be well worth if for the increased vehicle control and transmission longevity to me.
As for T/H and engine braking burning up a trans. I have never heard that one and yes, I used to be a truck driver. Engine braking by downshifting a transmission is practically required in any truck driving situation I ever encountered. That's why the T/H function (with grade braking as Chevy calls it) was created.
My '05 Chevy has 181,000 miles on it, I've owned it since new. I use T/H 80% of the time, often to slow down even when I'm not towing. The truck still has the original brake pads. I get my Allison transmission serviced every 25,000 miles. The tech said he couldn't believe how clean it was with so many miles on it.

Tow/haul holds each gear longer so you should use more fuel. In other words instead of shifting into 6th at 1800rpm it might do it at 2000rpm. Th higher the rpm, the more fuel is used. I leave it off unless the truck is frequently hunting gears or if I need it for engine braking.

[wrenchbender]

I have no difference in economy using T/H mode. I do not engage it on long freeway runs if the terrain is hilly,I get tired of it hunting.

[oldtrojan66]

Of course everyone's driving situation is different. I have had only a little experience with the T/H on my F350. The times I have towed, I have used the T/H feature, BUT I was heart-in-throat when I used the foot brake to slow down on a hill and the tranny shifted to a very high RPM. I mean screamin'! I turned off the T/H to get the engine down to a more normal sounding speed. I'm about 20K, truck and trailer, loaded but not a big load. I have found times when I turned the T/H off and felt more in control of towing than with it on. (Please, no flaming!, Just my opinion)

[coolbreeze01]

Use T/H as needed. Let the engine and transmission do their job with your input and your brakes will stay cool.
If you don't have an exhaust brake, get one.

[KD4UPL]

I don't understand all the reluctance to use a feature like T/H. It's there specifically to help the vehicle perform better under towing conditions. Why try and second guess the engineers and the manufacturer.
There's no logical reason that using T/H would lower your fuel mileage. It doesn't change your weight, wind resistance, vehicle speed, or gear ration. It just changes how the trans. shifts. Even if that did lower your mileage something like .01% it would be well worth if for the increased vehicle control and transmission longevity to me.
As for T/H and engine braking burning up a trans. I have never heard that one and yes, I used to be a truck driver. Engine braking by downshifting a transmission is practically required in any truck driving situation I ever encountered. That's why the T/H function (with grade braking as Chevy calls it) was created.
My '05 Chevy has 181,000 miles on it, I've owned it since new. I use T/H 80% of the time, often to slow down even when I'm not towing. The truck still has the original brake pads. I get my Allison transmission serviced every 25,000 miles. The tech said he couldn't believe how clean it was with so many miles on it.

[Mike_Taverniti]

I actually get better MPG. Always use Tow / Haul.

[Monaco_Montclai]

always turn it on WHEN towing.