Tow/Haul

[NewBlackDak]

In your Cummins Ram, T/H boosts the line pressure a bit. It helps make the shifts a bit quicker, hold gear a little longer, and keep the torque converter locked up. Depending on year model it might lock out the top overdrive gear(this might be your big mileage difference).

Your trailer is small potatoes for the truck, so it might not need T/H. I don’t even use it for my 6.4 RAM. I hate the way it shifts. It tries to hold 4th gear for way too long then lugs down, and looses all the momentum. It does much better if I just manually shift it.

[Jagiven]

I do not know a lot about diesels in general. Tow haul mode is generally the same across all vehicle platforms. I looked up your TT, and I bet your RAM 1 ton is not stressed with a 10K pound TT behind it. It is just another day in the park for it.

The key thing about the tow haul mode, is it keeps your engine and transmission optimized for max torque, which gives you the best towing performance. But there is always a compromise, which usually is fuel economy. It also usually drops you out from being able to use overdrive. It also commonly allows you to engage the engine braking ability, but it sounds like that will still work for you when not in tow haul mode.

I would monitor the temps, check the fluid conditions periodically, and run without tow haul mode on, unless in the hills or have a nasty headwind. It may also be nice in stop and go traffic.

[Mikayles]

Spower,,,,it would help if we knew which transmission you have. There are two offered in the RAM 3500. The Aisin or the 68RFE. On my 3500 with the AISIN tow haul makes the shifts solid .....you can manually change or limit what gear you are in or want with the + or - buttons on your steering wheel. The gear you are in will show up next to the PRND indicator. Some RAM trucks have this feature on the transmission stalk depending on the year of your truck. Hope this helps. On my truck tow haul in conjunction with my exhaust brake works great at slowing the combination down.

[DocBrown]

Originally Posted by Spower

How is it straining it if it isn't running any hotter or shifting more than when in tow/haul?

Well, that's the trick isn't it? Keeping it from shifting and heating up. In theory you can run all day in a "normal" gear and not hurt the transmission if it's not shifting and heating up.

The trouble becomes grades, even slight ones, and wind. I've towed a lot of miles, trips out west and down south. The only flat place I've towed is I-80 across norther Nevada. And 90% of the time I find myself towing into the wind. Granted your diesel can handle things better than my 1/2 ton. Keep in mind too that tow/haul mode changes your shift points and lets it wind out farther to take advantage of the torque from a dead stop.

So if you think turning off tow/haul mode is working for you, don't let any of us tell you otherwise. I do think we'd all be interested in a report a year from now to see how you are doing with it.

[Scott_Trailer_Newbe]

Don’t mean to hijack but on the subject of the 68RFE. My one issue with this transmission is going down 7-8% grades towing and in tow-haul mode. Can’t remember which gear (2-3rd?) going down the grade the exhaust break is doing fine but the transmission wants to aggressively downshift and now I’m going too slow. Press on the Gas peddle a little bit and back to where I want to be, low RPM and exhaust break doing its job. Gain just 1-3 MPH and back to the aggressive downshifting and now I’m going too slow again. I don’t even have a chance to apply just a little break to make the transmission happy.

[Lake Huron]

If you are on the highway, you can test your t/h mode to see if it's even doing anything for you. Depending on your highway speed, run it off and see what your RPM is at. Then turn it on and see if your RPM increases. If you dont see any change, it's not going to matter and your MPG will be the same regardless. My Duramax in t/h doesnt do anything above 60 or 65, cant remember, other than keeping the same speed going downhill. It then keeps the converter in lock up and downshifts if needed. I do notice a difference as it enhances the engine brake.
You can also keep an eye on your trans temps. If you're going slow enough speeds and not in t/h mode, your trans may be in a higher gear and if the trans temps get high, it's essentially slipping. Slipping causes friction which causes more heat. That's when you need t/h mode to keep it out of the higher gears and keep the clutches locked up.
I will say while towing it is thirsty for DEF. I can also tell when it goes into a regen mode because I can watch my MPG drop quickly. I'm running a fuel additive in it to help keep the fuel system lubricated and put some BTU back in the fuel which helps lessen the regens.
Another thing I've noticed is my MPG is bad when I tow heading west or north here in michigan. Towing back east and south I get better MPG. Only thing I can figure is headed west I'm running into a head wind and north I'm going uphill.
My Cummins on the other hand is an older one and I've found with it there is a sweet spot with the speed to get the best mpg. It seems it likes about 72-73 mph. I've found running any faster it gets poor mileage be cause its turning faster RPM. HOWEVER, running at a slower speed, I also get lower MPG because it's got the engine lugged down too low and it's not running very efficiently. T/H mode with that truck works up to 60mph. After that its useless.
Now that I've made it clear as mud for you, ... lol!
Try some different things and see what happens.

[hummy]

I only use it when I need more pulling,steering,or stopping power. All depends on your load when to use it

[TxLoser]

Originally Posted by hummy

I only use it when I need more pulling,steering,or stopping power. All depends on your load when to use it

Steering? Curious about this one. I don’t think with any manufacturer it does anything for your steering capabilities, but I’ve been wrong at least once in the past.

[hummy]

What i mean about steering is "you" have more control

[Slurugger]

Originally Posted by Spower

How is it straining it if it isn't running any hotter or shifting more than when in tow/haul?

Just an observation, make sure your Ram is telling you the actual trans temp and you're not simply using the trans temp needle to arrive the conclusion of "it's not running any hotter". In my experience with my Ford, 10-20 degree changes don't reflect change on the needle gauge but obviously have an impact of your transmission...

[curver900]

if it isn't hunting you can save yourself some fuel... You can read your manual and it will tell you exactly what the T/H function does for your particular vehicle... start there...

[dhinkle57]

I hate tow/haul in my f150 in the hills of southern Missouri. Down one hill then up the next the trans waits too long to down shift, losing momentum and may even shift down three gears and really rev the engine. I've learned to manually shift it as we start to go up hill to keep the revs steady.

[Boooker]

My Sierra has it too. Reading my owner's manual it tells me if the trailer is lightweight you may not see the benefit of using Tow/Haul Mode. I believe it says optional for trailers under a certain weight.

[Mikayles]

My suspicion is her trans is limiting the upshifts to 5th gear in towhaul....It's why I asked what trans she has. Easy to identify on a Ram as the 68RE the dipstick is on the left....The Aisin it's on the right when looking at the engine from the front. My 2019 truck gives me the option of all gears in TH mode or limiting the upshifts to whatever gear I chose with the Aisin trans.

[Pickledill]

In flat and gently rolling hills once up to speed I do not use tow/haul either. It typically has a tendency to keep transmission one gear below optimal for fuel effeciency. If engine is not lugging, and transmission isn't hunting between top gear and 5 or 9th whichever applies, dont feel the need to use it. You must be attentive to your driving environment and understand how it works. It sounds like you will figure it out based on your questions. For the rest, tow/haul mode all the time when towing which is fine by the way. No flaming please!

[Mikayles]

Originally Posted by NewBlackDak

In your Cummins Ram, T/H boosts the line pressure a bit. It helps make the shifts a bit quicker, hold gear a little longer, and keep the torque converter locked up. Depending on year model it might lock out the top overdrive gear(this might be your big mileage difference).

Your trailer is small potatoes for the truck, so it might not need T/H. I don’t even use it for my 6.4 RAM. I hate the way it shifts. It tries to hold 4th gear for way too long then lugs down, and looses all the momentum. It does much better if I just manually shift it.

Just for kicks I took my truck out today and used towhaul mode. It does shift much firmer and held 5th gear to 60 mph. I haven't towed with the truck yet but will next week.

[Drew A.]

Originally Posted by Spower

Hi All,

So my truck (see signature) has tow/haul mode. I have always used it when towing. My understanding is it will shift less using a higher RPM (in a nutshell).
Now that I am a full timer on the road I am learning a lot of things.
I noticed my mileage was really bad! Like 8 MPG, and just drinking the DEF like crazy. Some of this was due to some headwinds, hate the wind. Anyway, stopped to fuel up and got back on the road. I forgot to turn tow/haul back on. And guess what? My mileage was up and staying between 12 - 14 MPG. That is a big difference! The RPM's were lower. Nothing was running any hotter than usual (tranny/oil) it wasn't shifting any different either. And it stopped gulping the DEF.
So I am going to run without if for now, I will use if for any long uphill grades.

What do you guys think? Do you use it (if you have it)?

Hi, I have essentially the the same truck as you do, only difference is mine is a short bed. I ran tow/haul exclusively last year on a trip from MA to TN and back. I did not experience poor mileage or excessive DEF usage on that trip. As a matter of fact, the hand calculated mileage on that trip was around 12 MPG. I'm towing a 2010 32BHDS that's pretty close to GVW of 9500 pounds.

Maybe your experience was a fluke and more to do with the headwinds than the use of tow/haul.

Good Luck

[Spower]

Originally Posted by Drew A.

Hi, I have essentially the the same truck as you do, only difference is mine is a short bed. I ran tow/haul exclusively last year on a trip from MA to TN and back. I did not experience poor mileage or excessive DEF usage on that trip. As a matter of fact, the hand calculated mileage on that trip was around 12 MPG. I'm towing a 2010 32BHDS that's pretty close to GVW of 9500 pounds.

Maybe your experience was a fluke and more to do with the headwinds than the use of tow/haul.

Good Luck

So I've done about 1500 miles since I posted this using tow/haul....mileage and def got way better, so yeah, maybe winds, hills, the angel of the moon? I dont know but on the advice of most of you guys I will continue to always use tow/haul while towing 😉🍻

[jkkinder]

We are thinking of getting a trailer to tow our 1931 Ford Model A. Does the E450 have anything like a tow/haul switch? Sorry I'm a lady no mechanical experience! LOL

[Mad5581]

I used to not use my tow/haul and my old truck did just fine pulling without it. Like you I got better MPG without using it. Saved a few $ on gas. At 120k miles I was also in the transmission shop at the dealership. End result was new 1,2,3rd gear clutch pack, new torque converter. $3500 later lucky for me I got GM to pay 2/3's of the bill. But I talked to the transmission guy at the shop and he said 20 years working on the HD GM transmissions and mine was in the top 3 of worst he had ever seen. He flat out asked if I used tow/haul mode. I was like no. He said anything over about 2500 lbs behind you and you should always use it. Its almost like having a shift kit. It cycles the clutches faster and locks the torque converter up faster. Less slippage is good. He said you may not even really feel like it's doing anything but it is. It also increases line pressure to move more transmission fluid around for cooling and lubrication. The lubrication is the key. That you dont see on the temp gauge really. The transmission tech said flat out you will prematurely burn up clutches and the torque converter if you dont use it. That was 10 years ago and the newer transmissions are more like $5k to $8k to rebuild. That's a ton of extra fuel to burn. Oh and DEF is used based on your fuel consumption. So if you loose fuel economy you will automatically use more DEF. And honestly it's a lot more DEF. I normally get 5k to 6k miles out of a tank of DEF but pulling my 43 footer it drops to 2k miles for the same tank. Not pulling I get over 20mpg, pulling it gets 12 to 13mpg. Hope this all helps answer your questions.