Gear Ratio change

[SnoKing]

I think 16mpg is pretty good for something that weighs over 4 tons. My truck comes in in two days and I got the 4.10. In the back of my mind I'm thinking the 4.10's are going to be a challenge since unloaded I drive a lot faster than 70. On my 2nd gen I have the 3.54 gears. When I tow I get 14mpg, when I'm empty I get 10mpg. You decide how I get such "bad" fuel economy when 12,000lbs lighter.

Your neighbor is stealing your fuel! SNOKING

 

[NDanecker]

My 13 had 3.42 and the 68rfe. When towing heavy (north of 25k gross) I had a difficult time getting the rig moving. Once moving on the highway I kept it in 5th which is similar to 6th with 4.10. I couldn't deal with the gearing so traded in the '13 for a '14 with AISIN and 4.10s. With the lower 1st gearing of the AISIN and 4.10 I barely need to throttle it to get the same heavy load moving. Unless you've driven the two to compare you will not understand, and will say the 3.42 tow the same as 4.10s. I call BS.......:-laf

I'm vary happy with the 4.10. My overall mileage between the two is pretty much the same. I know people say the 3.42s get way better mileage and they do on the highway but once you factor in real world mixed driving the true average is the same (check out my fuelly logs between trucks).

My suggestion is to get the 4.10 and not worry about the mileage because they will be pretty much the same on average (at least they were for me .... same driver.....same commute....etc.)

Good luck....

 

[Newsa]

With a 4x4, wouldn't you need to refer both front & rear axles?

 

[Bug Out]

I was not thrilled to go from 4:10's in my 2012 -3500 dually max tow to 3:42;s in my 2013. But I have to say, once you get to 5-8mph, its all the same, or at least it felt like it to me. I tow a 40' 5th that weighs in at 17K. My 2012 with 4:10's did launch a bit better, as far as RPMS go, but the 2013 held its own. If you have the $ for the swap and feel the need, go for it. I'd do it to and like Cummins says, 5th gear with the 3:42's mirrors what RPMS you'll have with the 4:10's @6 gear at freeway speed. Forget the 20MPG+ reading on the dash once you get 4:10's. One other thing I gave a lot of thought to, the % of towing time your doing? I tow maybe 20% of the time, 80% farting around...Now if I towed 80 and farted 20%, 4:10's would be in ASAP....JMHO

 

[photowrite]

With modern machining, oils, and ECM's I doubt there is even a 1.5 mpg difference let alone 3mpg. Modern engines just don't burn enough more fuel at increased rpms to make that difference, especially considering the engine has a 20% mechanical advantage.

There will be a increase in fuel burn, but aside from fleet use I am not sure it's enough to write home about.

I think this is the first time I've read a post/opinion of your's where we disagree

Agreed the mechanical advantage of the lower gears helps (I love it in my gas rigs).

I'd be very surprised if a repeatable, back-to-back, unloaded driving fuel economy test was performed with an effort to limit variables (freeway only, cruise control, etc.) if a gear swap from 3.42:1 to 4.10:1 didn't result in at least a 1.5 mpg reduction.

Though maybe the top gear ratio is so tall with the A/T that the RPM difference in 6th is small?

 

[AH64ID]

At 75 mph the difference is 350 rpms, but event the 4.10's are under 2150 at 75.

Both trucks will require the same horsepower to go that speed and the truck with 4.10's can make it easier at 2110 vs 1760 but there will be slightly more parasitic drag. In the end I would expect the 3.42's to get slightly better mileage, but 1.5 seems high. A 3.42 truck at 75 could peak at what 17 mpg? 1.5 of 17 is nearly a 10% drop and I just don't see it being that high with the OD ratio of 6th.

I would like to see a side by side test thou.

Loaded I think the mileage could be better, so the ratio of loaded:unloaded would result in a net loss or net gain.

 

[moparnut72]

I just did a 1300 mile run empty with most highway running at 65. My EVIC showed 19.1 for the majority of the run. It was only at the end for the last 100 miles slow driving climbing 3500 feet that it dropped to 17.5. I don't know if my truck will show on a quick reply, but it is a 2013 dually with 4.10's. I am glad I have the 4.10's, small price to pay in lower fuel mileage for all the other benefits.
kk

 

[photowrite]

Loaded I think the mileage could be better, so the ratio of loaded:unloaded would result in a net loss or net gain.

I'm inclined to agree.

 

[134x4ctd]

Sorry for the late reply. Thank you for all of the responses. I decided to go on a long 1000 mile trip to see if I still felt that the ratio is too high. After all of that driving over northern California, I had several occaisons that I would drive slower than 20 mph through mountains and had to stop on a hill and take off again. The truck does go but it takes a lot of gas pedal and it seems as is I am taking off in second gear. I would like to change ratios. I am looking for any other info I can get on the trans programming. One shop has told me that once I get the gears changed I need to visit dealer to have the transmission re-programmed. I talked to my dealer and they werent sure. I know that the trans has a speed sensor and the driveshaft will be spinning faster so it makes sense. Any info would be appreciated. Thank you

 

[AH64ID]

Generally reprogramming after a gear change is for the speedometer which isnt required anymore. You shouldn't require anything be reprogrammed.

 

[EHoxie]

Just did my first highway run unloaded on 2015 3500 SRW aisin 3.42s . 390 miles total about 20 of those were on back roads the rest were a pretty consistent 70 mph. Hand calculated 21 mpg, EVIC indicated 22.1 mpg. My normal towing of 6000 lb trailer 20% highway 80% secondary roads I get 12.6 mpg calculated, EVIC shows 13.
My 2012 with 68rfe and 3.73s got 11 mpg towing and 16.5 unloaded highway.

 

[Deleted member 995608]

^^I agree^^

People on forum 'B' have swapped R&P's with any changes to the programming. It's one of the very few mechanical things left on these trucks.

 

[134x4ctd]

Thanks. Anybody out there with 3.73 ever have an issue with starting on a hill w/1200# trailer? I am thinking this is the way I will go. I have found a shop that can do this work at a reasonable cost.

 

[134x4ctd]

Thanks. Anybody out there with 3.73 ever have an issue with starting on a hill w/1200# trailer? I am thinking this is the way I will go. I have found a shop that can do this work at a reasonable cost.
Typo 12,000# trailer

 

[AH64ID]

Thanks. Anybody out there with 3.73 ever have an issue with starting on a hill w/1200# trailer? I am thinking this is the way I will go. I have found a shop that can do this work at a reasonable cost.
Typo 12,000# trailer

Just my 0.02, but I would go 4.10's if you are spending the money. 4.10's will give you a 20% incresae in rear wheel torque over 3.42's.

 

[ILIANBG]

I was looking at 2015 ram 3500 SRW, but i don't like the 3:42 only option. Hopefully they change that for 2016. I would like to get 4:10 or at least 3:73. We should have a choice with these 2500 and 3500 trucks. They are so much more expensive now, but we can't even get them geared for our needs.

 

[RVTRKN]

The option, or non option, is EPA's pressure on the auto manufactures, so don't expect it to change. If sales dropped off due to it, that would change their minds in a hot hurry. If you don't like the 3:42's, which I don't, then you have the dealer change it to the ratio you want, to maintain some kind of warranty protection before you take delivery or have a work order in hand when you take delivery. That way it can be worked into the deal and the cost would be included in the financing.

Then the next discussion should be, is 3:73 or 4:10 ratio the way to go? Back when it was the only option, your choice should then be determined by the planned use of the truck. If your going to occasionally tow heavy, then 3:73 should be your choice, but if your going to tow heavy more than 50% of the trucks life, then 4:10's should be your choice. I like my 3:73 choice in my 07 C&C because I rarely pull heavy, but when I do pull heavy I have some regret. If I were to do it all over, I would choose the 4:10.

 

[RustyJC]

We use our truck almost exclusively to tow heavy (see signature), and we went with the 4.10s. With the double overdrive 68RFE and Aisin transmissions, unloaded cruising at 75MPH is no problem with the 4.10s, unlike the 4.10s in our previous 2002 3500 ETH/DEE (NV5600 6-speed manual). A lot of people have experience with 4.10s in conjunction with the single overdrive 5 or 6 speed manual transmissions or the single overdrive 47/48RE automatic and write them off, but they are a very versatile all-around gear ratio with the 6-speed automatics. It's like having that 7th gear that I always wanted to reach for with the NV5600 and 4.10s.

Rusty

 

[rscurtis]

I thought about changing my signature truck from 3.73's to 3.42's, but did the math and it just wasn't worth it for a 9% RPM reduction. 3.42's would have been perfect for me, as the truck is used almost exclusively for unloaded travel.

 

[photowrite]

Just my 0.02, but I would go 4.10's if you are spending the money. 4.10's will give you a 20% incresae in rear wheel torque over 3.42's.

Strongly agreed! I would probably like/prefer 3.73:1 gears, but likely won't change my current setup. But if I was going to spend the money, I want a bigger change and would go with 4.10:1, even with a manual transmission.