Tow/haul mode always when towing?

[SD Rebel]

I also have the 5.7 (no E Torq) with a 3.92 and with it in tow/ haul, the MDS does work a few times. It will also hit 8th gear occasionally on level ground. This is with it towing a 5000lb boat.

You are the first I've heard say that. I run tow haul all the time and I have never seen MDS come on, no matter how easy I drive.

As for 8th gear, Tow Haul shouldn't prevent that, it just holds gears longer

Maybe it's a year or trim variation in regards to your ECO light turning on when in Tow Haul?

 

[theblet]

You are the first I've heard say that. I run tow haul all the time and I have never seen MDS come on, no matter how easy I drive.

As for 8th gear, Tow Haul shouldn't prevent that, it just holds gears longer

Maybe it's a year or trim variation in regards to your ECO light turning on when in Tow Haul?

I was thinking the same thing. I've never seen mds kick in with tow/haul enabled.

 

[silver billet]

I also have the 5.7 (no E Torq) with a 3.92 and with it in tow/ haul, the MDS does work a few times. It will also hit 8th gear occasionally on level ground. This is with it towing a 5000lb boat.

If you're truck is towing a 5000lb boat and that is preventing you from hitting 8th gear for the most part, there is no way MDS is activating. Just not enough grunt in 4 cylinder mode to pull that kind of load.

My truck will deactivate MDS with zero load just going down rural roads with no wind in 8th gear. If it hits a fly on the windshield, that's enough to pop it out. No way are you using MDS while towing that load straight and constant.

 

[bigdodge]

I also have the 5.7 (no E Torq) with a 3.92 and with it in tow/ haul, the MDS does work a few times. It will also hit 8th gear occasionally on level ground. This is with it towing a 5000lb boat.

a picture with the eco lite will go a long way proving your statement

 

[Trooper4]

I use tow/haul mode every single time I hook onto a trailer. Main reason is to keep the MDS system off. Shock loading the valvetrain is bad. Shockloading it with a big load on it is just asking for trouble. I had a 5.7 in a Challenger that had the recall for broken timing chains due to the MDS system and people putting their pedal to the floor a lot. Same concept happens when towing a large trailer on the highway, my truck will use every gear from 3 to 7 and it's important to keep the MDS junk turned off.

I tow heavy and in tens of thousands of miles I have seen MDS
/ECO activate happen maybe twice on a downhill with a tailwind. And anyone who hammers the gas when towing is just wasting gas to hear the exhaust note.

 

[Trailwalker16]

I Tow a 30 ft 6,000 lbs Travel trailer I put the tow / haul mode on . The downside is the mpgs . I ger about 8.5 which sucks. Im thinking of turning off the tow mode to see if I can get a mix of at least 10 between the 2 modes

 

[silver billet]

I Tow a 30 ft 6,000 lbs Travel trailer I put the tow / haul mode on . The downside is the mpgs . I ger about 8.5 which sucks. Im thinking of turning off the tow mode to see if I can get a mix of at least 10 between the 2 modes

I wouldn't do that! With that load you definitely want to use TH and leave it on, worrying about MPG is the wrong thing to do when towing. Let the engine rev and work as it needs to, they're built for it and will only build heat trying to lug in a lower gear.

 

[Rick3478]

You are the first I've heard say that. I run tow haul all the time and I have never seen MDS come on, no matter how easy I drive.

As for 8th gear, Tow Haul shouldn't prevent that, it just holds gears longer

Maybe it's a year or trim variation in regards to your ECO light turning on when in Tow Haul?

I've never seen ECO on mine, and 8th can happen at about 70 MPH empty.

 

[Trailwalker16]

I wouldn't do that! With that load you definitely want to use TH and leave it on, worrying about MPG is the wrong thing to do when towing. Let the engine rev and work as it needs to, they're built for it and will only build heat trying to lug in a lower gear.

Thanks, I appreciate the advice.

 

[Mr.Grid]

I Tow a 30 ft 6,000 lbs Travel trailer I put the tow / haul mode on . The downside is the mpgs . I ger about 8.5 which sucks. Im thinking of turning off the tow mode to see if I can get a mix of at least 10 between the 2 modes

I’d try it to see what the results are. You won’t/ can’t hurt anything trying this. Imho your 3.21 gear isn’t optimum for mileage when towing, as it increases the rpm spread between the upper gears.

I‘m towing a 7000# 24’ enclosed car hauler (29’) with 3.92 and no longer use Tow Haul. I’ve used it initially (several trips), and don’t see any advantage over not using, with the exception of steep downhills if you don’t want to do the manual down shift which doesn’t bother me. Mine will do 10 – 11 mpg flat towing and I run premium fuel towing the Appalachians.

 

[silver billet]

You won’t/ can’t hurt anything trying this.

Actually you can build up extra heat by lugging and extra shifting in the transmission

Imho your 3.21 gear isn’t optimum for mileage when towing, as it increases the rpm spread between the upper gears.

That's not correct. The upper gears have almost zero differences, it's the first and second where the difference is. In other words, the 3.92 only feels stronger immediately off the line. Once you're in the city or on the highway there is pretty much zero difference.

Gear ratios are still widely misunderstood it seems.

 

[Mr.Grid]

.........................3.92......... 3.21
x1st 4.71 18.46 15.11
2nd 3.14 12.30 10.07
x3rd 2.1 8.23 6.74
4th 1.67 6.54 5.36
x5th 1.29 5.05 4.14
6th 1.0 3.92 3.21
7th 0.84 3.29 2.69
8th 0.67 2.62 2.15

Above is the actual ratios of your drivetrain going down the road. 1st, 2nd, 3rd are not even in this towing at highway speeds discussion. The 3.21 is always running 1 gear behind the 3.92 towing at highway speeds. A 3.21 towing 7k# will probably never if ever get out of 6th gear at 65mph flat towing. A 3.92 gear will never get out of 7th gear.

With 3.92 and 4WD I tow 7k# with trans set to 7th gear no TH. If I had 3.21, I set trans to 6th gear no TH.

While mostly flat towing, Tow Haul does not let my trans get to 7th gear, needlessly holding the trans in 6th for long periods of time before allowing shift to 7th. Even after making the shift to 7th in TH it comes back out to 6th way too easy and then stays there for an extended period.

Me not using TH vs using TH when towing has NO effect on the engine/ trans temp flat towing. When the trans needs to be in a lower gear because of load, it drops down to the lower gear it needs to maintain speed that cruise control is set to, exact same as using TH. My trans / engine runs same temps not using TH as anyone else using TH. No hotter, no cooler.

As another here wrote…..” I've never seen ECO on mine, and 8th can happen at about 70 MPH empty”.

In 1/2 ton trucks, 3.21 gears are city to 50 mph driving empty vehicle imho. 3.21 spend more time shifting back and forth between 7 -8 than 3.92 @ 65+ mph empty.

 

[silver billet]

.........................3.92......... 3.21
x1st 4.71 18.46 15.11
2nd 3.14 12.30 10.07
x3rd 2.1 8.23 6.74
4th 1.67 6.54 5.36
x5th 1.29 5.05 4.14
6th 1.0 3.92 3.21
7th 0.84 3.29 2.69
8th 0.67 2.62 2.15

Above is the actual ratios of your drivetrain going down the road. 1st, 2nd, 3rd are not even in this towing at highway speeds discussion. The 3.21 is always running 1 gear behind the 3.92 towing at highway speeds.

No. It's running one gear number, but the gear ratio is almost identical.

And on the highway, the spread between gear ratios is minimal. First and second is a large jump between ratios, second and third still significant, but beyond that they're all small jumps. Each successive gear change has less and less drop in RPMs, meaning, the RPM spread decreases between the upper gears, not increases like you stated.

BTW your calculations are incorrect. 5th gens use the 8hp75 which has the following gear ratios. Note the color coded cells, see for example the two blue numbers, how close the 3.21 in 6th is to the 3.92 in 7th, that's literally "the same gear ratio" though obviously different gear numbers. This means that when you're pulling a load in 7th, my RPMs and engine power will match exactly to yours, only I'm in 6th. Similar things going on with the other color codes.



You're welcome to lug your engine, the facts remain that N/A engines build power more efficiently at higher RPMs. Lugging an engine builds heat. Those are the facts.

 

[silver billet]

In 1/2 ton trucks, 3.21 gears are city to 50 mph driving empty vehicle imho. 3.21 spend more time shifting back and forth between 7 -8 than 3.92 @ 65+ mph empty.

A 3.92 shifts more in the city. You will hit second gear sooner, third gear sooner. Stop and go traffic, same thing, probably one extra upshift and one extra downshift every time you go from 0 to 40 mph, remember the 3.21 is generally one gear number behind the 3.92 as you get above third, which means you're using more gear shifts to get to that speed all the time.

On the freeway the 3.21 has an extra shift. It generally stays there unless you hit a steeper hill.

Pros and cons.

 

[SnowBlaZR2]

Someone say 3.21 vs. 3.92?

 

[WXman]

So I had a ’20 with EcoDiesel and 3.92 axle ratio. On paper this truck should have been a beast.

Today I have a ’22 with Hemi and 3.21 axle ratio.

What I tow is a 8.5x20 enclosed trailer. Been towing this size trailer with both trucks over the last few years. The trailer while loaded goes somewhere in the ballpark of 6,000 lbs. The frontal area is 56 sq/ft which is within spec for a ½ ton truck.

The roads I travel are a mix of two-lane 55 MPH roads, four-lane 55 MPH roads, and 4-lane 70 MPH roads. There is only a small amount of city driving at the beginning and end of our trips.

What I have seen in the real world is that the 3.92 diesel truck would use 4th gear on the worst hills climbing grade, 5th through 7th most of the time, and 8th in perfect conditions or going downhill. The 3.21 gas truck uses 3rd gear on the worst hills, 4th through 6th most all of the time, and I’ve never seen it higher than 7th. In practice the trucks function exactly the same in terms of towing “feel” and performance in terms of transmission shifting. If I couldn’t see the gear indicator on the dash I’d never know there was a difference. My 3.21 gear Hemi truck has 35” tires on it and will still pull strong at low speeds or higher speeds. It’s quite impressive. (The 3.92 diesel truck had very similar size tires on it.) After driving both trucks extensively, the conclusion I have come to is that the biggest difference between the trucks isn’t the axle ratio, it’s the engine. GDE has told us through dyno testing that the EcoD makes 442 peak lb/ft of torque. It can only get that 480 number in 6th gear under only specific conditions. For all intents and purposes it’s a 442 lb/ft engine, which is ironically where the engine is rated in the Jeep pickup. Soooo… you’re really only looking at 30 lb/ft of difference between Hemi and EcoD…..BUT the Hemi absolutely trounces the EcoD in horsepower and to me that fact is very noticeable out on the road.

If I had my choice, I would go 3.92 gears every single time. 3.92s behind a Hemi engine would be awesome.

 

[SnowBlaZR2]

3.92s behind a Hemi engine would be awesome.

Can confirm.

 

[Mr.Grid]

Lugging an engine builds heat. Those are the facts.

That’s your Opinion. You’ve never towed in anything but TH. That is the Fact. This isn’t a manual transmission.

Towing without using TH does NOT lug the engine. The trans will downshift to the needed gear based on the engine load, Guaranteed! TH does nothing more than increase the rpm shift points and downshift points.

Towing the same 7k# trailer over 12k miles with this new 5th Gen 3.92 Hemi, the engine temperature is the same not using TH as it is using TH. That includes flat towing or towing 5.5% grade, TH verses not TH. That IS the FACT as I’ve personally experienced. Done it both ways.

That 2003 7k# trailer has well over 100k miles combined behind a 2004 3.92 Hemi Durango and 2011 3.92 Hemi Ram 1500, both with the 545 RFE, a 5 speed that is actually a 6 speed. Have used TH and not TH in both towing.

 

[CalvinC]

So sorry if I come off as pedantic, but "Lugging an engine builds heat." is most certainly a fact and universal truth.

Now, whether running your Ram 1500 DT without "Tall/Hoe" mode will result in said lugging, that can certainly be debated - and I assume that is the angle you are taking here.

 

[silver billet]

That’s your Opinion. You’ve never towed in anything but TH. That is the Fact. This isn’t a manual transmission.

Towing without using TH does NOT lug the engine. The trans will downshift to the needed gear based on the engine load, Guaranteed! TH does nothing more than increase the rpm shift points and downshift points.

That's incorrect. The lower the RPMs while towing, the more it lugs, the more it builds heat. That is a fact.

As you are already aware, TH changes the shift points, that means it changes when it shifts based on load. The same truck pulling the same load at the same speed, will probably drop to one lower gear the second you switch TH on and even slightly accelerate; and then it will hold that gear, either forever or for a much longer period of time.

Why do you think it does that? Two main reasons: your truck has more power at higher rpms, so less need to constantly down/up shift based on slight hills or changes in speed; this saves your transmission, as shifting builds heat. Second reason, your engine will run cooler at higher RPMs.

The entire point of TH is to use it when towing. It's literally called "tow haul". Let that sink in my friend, and use it for what it's there for. Towing a fishing boat, yeah not needed. A 5000+ pound RV, definitely use it. Your truck will run cooler and there is no gas savings letting it lug in a lower gear.