3.42 to 4.10

[GBBrown]

I've read a few posts where it is stated that if you shift down from 6th to 5th on a truck with a 68rfe and 3.42 axel, it's like having a 4.10's. I know the revs will come up but you still have a 3.42 axel. Sounds like apples to oranges.

 

[Cummins12V98]

Worked well for me towing a combined 29K.

 

[kthaxton]

I agree, it is apples and oranges. It works, but it is still not the same as having a lower ratio ring and pinion.

People often forget (or do not even realize) that there are two factors at play that make lower gears perform better...one, (that most people understand) is that puts the engine at a higher RPM and two (what many people seem to not know) is the mechanical advantage (leverage so to speak) that lower gears provide.

While I have no way to quantify it, I feel item "two" is the most important factor.

....and that's not even getting into all of the less-wear-on-the-drivetrain advantages.

 

[spoon059]

Like kthaxton said, your overall drive ratio might be similar, but gears 1-4 getting started will all be higher and not provide you as much "take off" power.

 

[RustyJC]

Like kthaxton said, your overall drive ratio might be similar, but gears 1-4 getting started will all be higher and not provide you as much "take off" power.

Nor will reverse be any lower - important when backing a 19K GVWR 5th wheel up a grade into a campsite.

Rusty

 

[kthaxton]

Nor will reverse be any lower - important when backing a 19K GVWR 5th wheel up a grade into a campsite.

Rusty

True, but on the flip side.....for us poor souls that are stuck with the horribly inadequate 68RFE , it's not much of an issue, since it has a super-low reverse ratio of 4.44:1.

 

[RustyJC]

Oh, it can still be an issue. My 4.10/68RFE-equipped truck was working fairly hard to shove our Mobile Suites up a pretty good grade into a campsite back on December 20th. It certainly would have been tougher with 3.42s.

(OK, cue the 4x4 boys with their "just drop it into 4WD Low Range" comments.)

Rusty

 

[kthaxton]

Well, that's what I would do. :-laf

 

[Cummins12V98]

After towing 29K combined for 65K with my 11 HO Dually 68RFE I knew 4:10's would be the way to go when I decided to get a heavier RV. I liked the 1650-1750RPM in 5th at 60 the same as the 4.10's in 6th. But taking off on much of a grade I took it easy. So if I were to limit my self to a 28K combined load I would buy the 3.42's with Aisin for sure. Any heavier 4.10's with Aisin.

 

[AH64ID]

It all depends on when you are comparing the two and how you tow.

6th to 5th at highway speeds is an apples to apples comparison.

0.63*4.10 = 2.583
0.77*3.42 = 2.6334 (Aisin 5th) 1.9% lower
0.82*3.42 = 2.8044 (68RFE 5th) 8.5% lower

So actually a 3.42 truck in 5th is slightly lower geared than a 4.10 truck in 6th with either transmission.


If you spend a lot of time at slower speeds then it's very hard to compare the two as 1st is as low as it gets.

 

[Jim W]

John, People do not want the fact's.

Also to me this there is no debate on what gear ratio to order if you buy a SRW truck equipped with the Cummins engine. Ram only offers one gear ratio and that is the 3:42 so except and let's move on. If you want a different gear ration than buy a DRW truck; end of story.

As pointed out to us that were at the TDR rally in Columbus IN., in 2013. Ram has done their testing and they have determined that the 3:42 differential ratio is all that is required for a SRW truck to tow within it's limits.

Jim

 

[gsbrockman]

(OK, cue the 4x4 boys with their "just drop it into 4WD Low Range" comments.)

It should be just fine......there's some reports that others use 4WD on wet roads to prevent hydroplaning. :-laf

 

[Cummins12V98]

It all depends on when you are comparing the two and how you tow.

6th to 5th at highway speeds is an apples to apples comparison.

0.63*4.10 = 2.583
0.77*3.42 = 2.6334 (Aisin 5th) 1.9% lower
0.82*3.42 = 2.8044 (68RFE 5th) 8.5% lower

So actually a 3.42 truck in 5th is slightly lower geared than a 4.10 truck in 6th with either transmission.


If you spend a lot of time at slower speeds then it's very hard to compare the two as 1st is as low as it gets.

When I rode with SNOKING I had him drop to 5th and his rpm at 60 was 1,650rpm. My 4.10's at 60 in 6th I am 1,750rpm.

 

[AH64ID]

When I rode with SNOKING I had him drop to 5th and his rpm at 60 was 1,650rpm. My 4.10's at 60 in 6th I am 1,750rpm.

DRW tire size vs SRW tire size.

The numbers I posted are drive ratio and based on the transmission hearing assuming a locked torque converter. Tire size is not a factor in my calcs, but the DRW tires are shorter and thus will increase rpms.

If you both had 275/70R18's the 4.10's in 6th would be 1617 and the 3.42's in 5th would be 1649.

Your torque converter must have been unlocked. With a locked torque converter a 4.10 truck with 235/80R17's should be at 1676 rpms at 60.

 

[Newsa]

It should be just fine......there's some reports that others use 4WD on wet roads to prevent hydroplaning. :-laf

Yup. Just fine. Had to drop into 4x4 low on dry pavement at Red Top Mountain State Park to back into a primo spot.

yes, the truck bucked, but rear wheels were spinning in 2wd

 

[Cummins12V98]

"Your torque converter must have been unlocked. With a locked torque converter a 4.10 truck with 235/80R17's should be at 1676 rpms at 60."


I will look again. Will take a photo, I know The converter was locked as it usually is.

 

[Shadrach]

The backing up part is why I installed Dyna Trac front hubs on my 03. Putting it in 4Lo and not having the front axle engaged on pavement was real nice.

David

 

[AH64ID]

The backing up part is why I installed Dyna Trac front hubs on my 03. Putting it in 4Lo and not having the front axle engaged on pavement was real nice.

David

I agree. The LOW gearing of 4Lo is just asking for trouble when used on dry pavement.

 

[Dogpatch]

I have to back my 15-1/2K 5th wheel up this road and up into the lot beside my house. I use 4 low but it backs that much weight up effortlessly. If you look the garage on the right in the first photo, you get an idea of the grade. I'm at the top of that road. Once it gets into my property and driveway the grade gets a lot steeper. Pretty impressed with the power and torque these trucks have!

 

[Dogpatch]

I hear mention a lot on locked/unlocked torque converters. I need some educating on this cause I don't understand. Does the truck do this on its own? Do I need to do something? This is my first experience owning this kind of truck. Long way to go!