Actualy, the blanket statement is correct across the board. The lower the leverage ratio is (gearing) the more effort the engine puts forth to move the load, irregardless of the final ratio.

Tow ratings are based more on what the transmission can NOT handle balanced by BSFC and expected life. Bottom line is the lower the load capability to maintain the other expectations. The 68RFE is under clutched and over managed just like all the rest, its simply a zero sum game when you start playing with gear ratios.

If one can live with the reduced capacity then great, but, its not a fair comparison to potential.

 

All I can say is that our 2011 HO with 3.42 gets about the same mpg as our 2004 w/Edge Juice & 4.10.
We have a '99 too w/3.73 but the problem is the 215hp/420ft. We should have put a juice on that one too but never got around to it. Now it's replaced after 311k miles.

 

The blanket statement I was referring too is that the 3.42 is for driving empty. when did towing 9,400lbs become synonymous with "empty". I know what you were trying to say. the fact remains that no matter which gear ratio these trucks have they are made for towing. The question is how much. IMO, the 3.42 is a perfect balance of mpg and towing for a 10k# trailer provided the HP/Torque is there. The 4.10 is great for 16k# and up, 5th wheel etc.
Technically, we could use a SRW but the DRW pulls so much nicer. Our '04 with 4.10 is such overkill for us pulling a 7k trailer and payload of 4k or less. I think I even heard her laugh at my trailer once. What's really funny is seeing this big truck pulling a little 15' seadoo jet boat.

Our 2011 HO with 3.42 pulls the our rig perfectly. Of course, 6th is used with caution but it is used, still getting used to it.
When I was researching online and looking through the forums, it was difficult to find the answers I was looking for. I read tons of comments of "only get the 4.10 or at most get the 3.73" Everyone has an opinion. But I was looking for the feedback of the guy who said I tried it and it failed. Well I couldn't find any of those but the comments from owners with the 3.42 all said the same thing, pulls under 10k with no problem. Well, now that I have one I KNOW the 9,400lbs rating is BS. I suspect it has more to do with the trucks final OD gear ability than it's true capability in the hands of a person that knows how to tow and select the correct gear. Maybe I'm wrong and you will pass me on the side of the road as I'm waiting for a tow truck but I'm not going to buy a truck for the less than 5% of usage needs. I have no plans to pull a 5th wheel so I don't see the opportunity to pull anything heavier than I already have. I'd rather slow down and down shift on hills than have to drive slower on the flats where I spend 90+% of my driving.

Bottom line, if fuel economy is important and your main usage is within the manufactures towing specs you will have no worries.
Just my $0.02.

 

Well I'm done with the trip. I've always read on here that the 'sweet spot' is 1800-1900 rpms. So, with my new gears I set the cruise at 65 which is right at 1900 rpms. Guess what? Gas mileage was worse! I ended up with 9.7 mpg.

I used to tow 65 mph at 2100 rpms and returned about 10.5

The trailer I'm pulling is a 24ft car hauler. It actually weighs in more like 8k (not 9k as I mentioned earlier.) I usually have another 1k in people and junk in the bed of the truck as well.

Here's the interesting part. On the return trip I decided to bump up the speed. I set the cruise at 70 mph which is about 2000 rpms. I stopped 4 times (didn't stop once on the way down) and ended up with 11.1 mpg. If I hadn't stopped all those times I'm sure the economy would have been even better.

So, here's all I can figure. When I was pulling at 2100 rpms I was burning more fuel than at 1900 but when I hit the hills (with cruise set) the truck didn't have to burn as much to keep up the speed. When I hit the hills at 1900 rpms the truck had to work a lot harder (burn more fuel) to keep the speed up.

As far as 1900 being the 'sweet spot', well not on my truck aparantly..grr.

Next tow isn't until Oct. I will definitely be driving at 70 and will report back my findings.

 

Now you see why the leverage of the gears is so important. You have enough weight there th enegine is just working harder to maintain speed than it did before.

Using the cruise did not help you any. Normally expect 1 to 1.5 increase by turning cruise off and just holding a steady throttle. The speed will drop on the hills but given your engine and gearing is tuned correctly it will roll with little extra load. The CC tends to want to maintain speed all the time and that uses more fuel.

Summation; 3.42' s really are for empty driving. Huh, maybe the Dodge engineers knew a thing or two.

 

I think what you are trying to say is that 3.42's in OD is for empty driving. However that would be like saying the 4.10 ratio is not for Highway driving speeds. It's the operators responsibility to pick the right combo of gearing. And from the data it appears he just needed more speed or pick a lower gear. But either way it still tows.
I just pulled 11,300# today with my 3.42 in tow/haul, so no OD. Hit the hill and the auto down shifted to 4th and still maintained 65mph. A dump trailer with 4.30 tons of gravel, you know, basically empty.

 

Looks like its pretty obvious what I meant. Kinda shoots holes in your theory that 3.42's and 8-10k is doable with the same efficacy, huh?

Wonder what 5-6k would look like? Any bets it delivers consistently lower mpg with 3.42's?

4.10's with a double OD is about as perfect a balance between efficiency and power there is, as the truck is delivered. Like several of us pointed out, just changing gears can sometimes be a net loss becuase of the way the engine wants to run.

 

Actually the gear changed proved to be more efficient. I can now drive 5 mph faster and saw a bit of a bump in fuel economy. I went from 10.5 to 11.1. This is also with a bunch more stops than I normally make. I would surprised without the stops if I couldn’t see 10% improvement.

Next time I'm going to do the trip one way at 2000 rpms and the other way at 2100 just to see what happens. It sure is nice being able to tow a bit quicker.

Overall I'm pleased. I saw an improvement in fuel econ towing AND I get to drive a bit faster. Will I ever get my money out of the gear swap –doubtful. But being able to tow faster, getting a fuel econ bump, and getting much better unloaded fuel econ are all very nice. Admittedly I don't drive unloaded often, but wow the truck is so much nicer to drive unloaded now.

 

It has been stated by Ram/Cummins engineers that the tow rating difference in 3.42, 3.73, and 4.10's is based solely on drivetrain strain. At any given weight a vehicle with 3.42s has to have more engine torque applied and for longer than the same vehicle with 4.10's. It's based mainly on acceleration.

5th with 3.42's is actually lower than 6th with 4.10's, but it's not the highways speeds where 4.10's shine, its the lower gears where the tow rating is really derived.


Do you have anything to quantify that?

My dad has an 06 G56 and I have an 05 NV5600, both have 3.73's so his 06 is geared like mine would be with 4.10's and our mileage (pre-mods) was nearly identical. Sometimes he would do better and sometimes I would. But at the same GCWR in hilly terrain his G56 seems to do a hair better due to the better mechanical advantage.

The E J/A doesn't add to flywheel hp, which your math indicated. They get 100/250 gain to the rear wheels so the flywheel increase is greater or the rwhp is lower. I would expect a E J/A to put down about 350/750 to the ground. If you are using the 04 for towing you will probably not like 3.42's and an Edge, it sounds like a very hot running combo!

I am really not surprised. The sweet spot on the VP trucks is that low, but not on HPCR's it's 2000-2200. There is a large difference in tuning at 2000 rpms, I can pull grades easier and at lower EGT's at 2000 vs 1900. The dyno's I have done verify this rapid tuning change at 2000.



I would also guess that you need to run a few more tanks to verify any real change. I vary from 10-14 on the same trailer depending on the area, direction of travel, weather, etc.

The lower gears means the motor has to make more tq to put the same tq to the wheels, so when towing it has to burn more fuel, time will really be what tells the story.

Empty driving may see a slight increase but HPCR's aren't nearly as rpm picky for fuel consumption as older style motors.

 

Exactly what I was expecting. Good news. After a gear switch, it's like learning to drive a new truck all over. We only use autos so that changes things a bit too. We had ruled it out before but are now actually revisiting the Gear Vendors add on again. After the Absolutely awesome performance of our latest 3500 with the 3.42 rear. The GV with a 48RE/4.10 has very similar rpm ranges for corresponding gears. We could make use of 3rd over and 4th over, essentially giving us a 6speed auto. Only drawback to GV is that it can't be used for towing in double overdrive but not a deal breaker as there is almost nothing gained in fuel economy but a quieter/lower rpm motor would be nice.

We have three Cummins diesel trucks with 3.42/68RFE, 3.73/47RE and 4.10/48RE. the 4.10 with out any disagreement pulls the best right up until it's on the highway at 75+ mph. The 3.73 happens to be in a 1999 with 215hp/420ft, so it's truely underpowered when we hit a steeper grade but level'ish highway driving, it pulls nice and sounds nice. the 2011 HO is the best of both worlds and even a little better.

Until you own a lower geared truck it's difficult to really know how it feels and even then there are so many factors that simply changing the tranny or stronger motor, throws previously held beliefs out the window. If we were towing over 10k on a regular basis, we would probably stay with the 4.10 gear in out '04.

 

Frankly, your not even making sense on your assessment. Loose mileage towing gain minimal mileage running empty. All for the perception it FEELS better??? Placebo mod for sure.

So far you have posted a net loss with a large investment up front. About the only thing that makes sense is you never will recoup the costs of the change. Now, how much more wear you are introducing has to be considered also.

Everything posted so far says LOOSE LOOSE situation. Ah well, to each his own style.

 

Its evident from almost all of your posts you are antagonistic towards anyone or anything that doesn't jive with your views.

I don't make sense? Did you even bother to read what I wrote? Honestly did you?

I clearly stated I DID gain fuel economy. And if I hadn't had all the stops I'm pretty sure I would have seen a 10% improvement. $2000 min in diesel fuel a year translates into 2 years to make my money back. (Yes that math is right when you factor in the cost of snth gear oil change I needed to do soon anyway) Oh AND I get to tow faster now. That's a helluva nice bonus.

As for unladen I saw an even bigger bump in economy. I had to baby the crap out of the truck to get 17.5 mpg highway. Now I can drive pretty carelessly and returned 20 mpg over two weeks driving. That's almost 20% improvement. I hardly ever drive the truck around town because the econ was terrible and the constant shifting was annoying. With the new ring/pinion fuel econ is close to my car and YES IT DOES FEEL BETTER. Markably easier to shift without jerking the truck from all the torque and YES the higher mph of each gear allows for lazier shifting. All that translates into me most likely using the truck more often because its a lot nicer to drive.

Anyway, I've restated this over and over. I can't make it any clearer. I'm not done playing with target rpms for towing and will also try towing up hills without the cruise to see how much of an improvement that makes. If you disagree with any of this great but don't expect me to justify your offhanded remarks with a response again.