3.42 Rear Axle

[SRich2015]

At what Speed 90mph??? Ya, if you run 80+ you may want to run 3.73's but for pulling heavy at 70mph 4.10's are great!! But this is my opinion and everyone is free to run the gears they want!!

 

[BossHogg]

I re-geared mine to 4.10
I hauled some cows with it the first time.

I'm curious, what did it cost to re-gear to 4:10s and is your truck four-wheel or two-wheel drive?
What is the typical weight of the cows and trailer you pull?

Thanks

 

[Donnie Straps]

It cost me $2,000 for both axles and depends on what I need to pull I have 4 trailers I use 3 goose necks and one bumper pull. I can hook to 5,000# to 15,000# depending on what I'm doing. I just like the way the truck feels when I pull with the lower gears. Feels strong and before it felt like it struggled. My tires are taller than stock so empty my rpm is at 1800 at 70mph and truck feels like it has plenty of power for hills.

 

[SyN]

Not going to lie - I would really like to drive a 2500 6.7L very similar to mine with 3:73s or 4:10s - pulling the same 12K lb trailer just to compare.

I've read a article along time ago stating the same info as posted above - Cummins and Ram both agreed 3:42s was Ideal for the 6.7L in the 2500 - to compliment the sweet spot of the torque curve of the 6.7L engine.

I have only towed 4 or 5 times with my new 6.7L and I did it in tow haul mode and never went past 5th gear @ 65mph and she pulled 10K-12Klbs effortlessly it seemed.
Temps were all in the ideal range & RPMs never were an issue.

But with that said: I towed mostly on flat interstate,all trips were around 273 miles round trip- No Mountain passes

I still in my mind would be interested in 3:73s w/Electronic Lockers.
Will I ever flip the bill to have this done - No!

I'll just keep both differentials serviced with fresh Gear Oil and Enjoy.

 

[Sloverado]

It’s pretty good gearing when with stock tires. I’d like to have 373 with larger tires but it isn’t a need.

 

[SyN]

I would really like to add a 4" lift possibly with the addition of 20x10" wheels with a lower profile wider set of AMP Attack A/T tires - the total cost is friggin Ridiculous! So that actually will Never happen!

I will stick with the skinny 20x8 wheels & 285/60R20 Attack A/T.

I don't want to effect the gearing ratio - especially if the wife picks a 15K lb Toy Hauler!

 

[Summit1]

Not going to lie - I would really like to drive a 2500 6.7L very similar to mine with 3:73s or 4:10s - pulling the same 12K lb trailer just to compare.

I've read a article along time ago stating the same info as posted above - Cummins and Ram both agreed 3:42s was Ideal for the 6.7L in the 2500 - to compliment the sweet spot of the torque curve of the 6.7L engine.

I have only towed 4 or 5 times with my new 6.7L and I did it in tow haul mode and never went past 5th gear @ 65mph and she pulled 10K-12Klbs effortlessly it seemed.
Temps were all in the ideal range & RPMs never were an issue.

But with that said: I towed mostly on flat interstate,all trips were around 273 miles round trip- No Mountain passes...

My first trip towing my (>8,000 loaded) camper with my Laramie 2500/6.7/3.42 Ram (~8,000# loaded) was through the mountains of TN and NC, and it performed flawlessly. The transmission (including Tow/Haul mode) does the work, as it should be. No problems going up and down those mountains, and even my fuel economy was reasonable. There is nothing I would change about my current stock setup, other than the OEM TransForce AT's which will go away next week.

 

[RamItFaster]

<----- picture of the new Ram for my Profile Pic. It's a beautiful little monster, with the new tires on she reminds me of the Tonka Truck i had as a kid. She pulls beautifully by the way, my father loves it towing his 24' Travel Trailer.

 

[OLEJOE]

I’ve got an 18’ with the 3.42’s/68rfe/6.7 also. I pull my 7K TT in 5th gear at 65 mph at all most 1800 rpm. I have also pulled it in 6th with the tow/haul engaged and it pulled it with ease. I know every area is different. Just rolling hills in my local. Glad to know where the “sweet spot “ is located.

 

[ticat928]

What I like about the 3.42 it decreases drive train HP loss due to less friction loss in the transfer of power to axles.

The steeper the gearing the smaller the pinion gear the less teeth engaged with ring gear the higher the contact pressure with the same load.

There is a reason the 3500 with 4.10 gears comes with a finned aluminum differential cover, it is to help with the additional heating of gear oil due to additional friction of the 4.10 vs. 3.42

 

[ticat928]

Here is what you said previously said; "3.42's have no place behind the Cummins!! IMO Yes they are good for fuel mileage empty on the highway"

They do it just fine. Like I said in an early post, I can easily reach 65 MPH on a freeway acceleration ramp pulling 15,000 pounds. You have never driven a RAM Cummins with 3:42 axle ratios pulling a 15,000 RV. How do I know this? Because of what you said. If you get the chance to drive one, you will be pleasantly surprised.

4:10s do not keep the Cummins in the sweet RPM spot any better than any other axle ratio since it is MPH based. First off, the Cummins sweet spot is 1,600 to 2,200 RPMs, these numbers come from the Cummins' Powerspec application (free to download and use). The RAM Cummins will pull at 1,850 RPM, 5th gear, at 65MPH all day, right in its sweet spot.

Depending on the frontal area of your RV towing in 4th gear is optimal for the 68rfe since it avoids the weak 5th and 6th gear overdrive clutch pack.

To me that is the main reason that 3.42 ratio is the best for towing , it extends the life of the transmission.

it also extends life of engine and turbocharger, at 2200 rpm with 15,000 lbs and large frontal area in a head wind, load on engine is less than towing in 5th at 1850 rpm

 

[stevenP]

Just bought a 18 2500, and its got the 3.42's. Drives just fine.

My 14 dually has 3.73's with the finned rear diff cover because its the H.O. version (385HP) . Pretty sure the finned covers only came on the H.O. versions with the aisin tranny option.

 

[Summit1]

This discussion of "rear axle ratio" (what about the front axle ratio? [emoji848] ) closely resemble those found on the RV forums and Faecesbook pages. A lot of folks want to re-engineer that on which millions of dollars' worth of R&D has already been done. The Cummins 6.7 TD, 3.42 axlew gearing, and 68RFE tranny will work just fine, and for a long time, and with heavy pulling (within the specs of the truck, of course). My experience is with a 2017 Ram 2500, now with almost 30,000 miles. I have no complaints. and no problems (not even issues) with any of it.


Sent from my iPad using Tapatalk

 

[Dennis Shellito]

I see the standard axle in the 2020 Ram 2500 CTD is back to the 3.73 ratio. I guess FCA has heard some complaints, but like I said that is just a guess.

 

[BossHogg]

I see the standard axle in the 2020 Ram 2500 CTD is back to the 3.73 ratio. I guess FCA has heard some complaints, but like I said that is just a guess.

Could be other reasons or a combo of reasons they went back to 3.73s, for example, they can up the towing capability. Maybe the 3.73s allowed more aggressive torque management providing the transmission less stress and longer service life.

I would love to be a fly on the wall in their engineering meetings.

 

[DMPlikesRAM]

I have a 2016 Ram 3500 Limited 4x4 crew cab short box SRW with 6.7l Cummins, Aisin trans, and 3.42 rear axle, with the 20 inch rims. I regularly pull a 40 foot fifth wheel that weighs about 15,000 pounds loaded. If I average 65 to 70 mph to save on fuel and tire wear, I get about 10 mpg. I live in Colorado, and regularly am driving above 4,500 feet and over mountain passes at or above 10,000 feet. Anyone familiar with Eisenhower tunnel on Interstate 70 west of Denver? I hit the tunnel after the long climb doing 55 mph.

I could imagine the 3.73 and/or 4.10 gear ratios might make acceleration and/or climbing even more effortless, but it might sacrifice on fuel economy somewhat.

I don't see a problem with this setup I have!

For this size trailer, I see no need for DRW either.

I've driven A LOT of trucks and trailers, and this is the most stress free, stable, economical and powerful combo I've ever owned!

 

[Jack P]

I have a question for Syn. Are the 285/70/20 the stock setup? My 2013 2500 3:42 came with 245/70/17. They look small. Everyone ask why I have such little wheels.

 

[Dennis Shellito]

I have a question for Syn. Are the 285/70/20 the stock setup? My 2013 2500 3:42 came with 245/70/17. They look small. Everyone ask why I have such little wheels.

The optional size for your 13 and my 11 is 265/70/17, which come on the Laramie. When I bought my truck ,my friend who used to be a mechanic at that dealer told me when I replace the tires I should move up a size from the 265 so it will look more normal. I haven't replaced all four yet and I don't want to throw my speedo off. I have had to replace pairs twice in the last 75,000 miles and hope the next time I can get a full set of 4.