Rear End Gear ratio

[Jayco]

I have a 2018 Ram 2500 4X4 powered with 6.4 gas motor.
The rear end gear is 3.73. Thinking about stepping up to the 4.10 gear.
If I change the rear gear do I need to change the gearing in the front?
What happens with the Speedometer?
Does the PCM need to be re programmed?

Help please...

 

[AFMoulton]

I have a 2018 Ram 2500 4X4 powered with 6.4 gas motor.
The rear end gear is 3.73. Thinking about stepping up to the 4.10 gear.
If I change the rear gear do I need to change the gearing in the front?
What happens with the Speedometer?
Does the PCM need to be re programmed?

Help please...

Yes you will need to re-gear the front. The speedo should be fine and it wouldn’t hurt to get an unlocked PCM with new ratio, not 100% sure you need it.

I will say this if you are going to spend the money ($2500-3000) to re-gear, then you should step up to 4.56/4.88/5.13. There won’t be much improvement from 3.73 to 4.10 sadly.

There are quite a few threads on here with guys who have 6.4 2500’s with re-gears done, and they are very detailed.


6.4 hemi, 4.56 gears, speed and RPM's
https://r.tapatalk.com/shareLink?sh...6-gears,-speed-and-RPM's.109503/&share_type=t


2018 2500 6.4 4x4 4.10 Amsoil SS 0w-40, Softopper
Black Rhino Arsenal 18x9 +12mm
Cooper St MAXX LT295/70R18

2016 Durango 5.7 AWD 3.07 Redline 5W-30 RP 10-48
1996 Nissan Altima 2.4 Amsoil SS 5W-30

 

[Jayco]

Thanks for the help. Kind of what I thought viewing a few UTube vids.
I’ll start searching for more 6.4 posts. Want to start personalizing the truck a bit with simple driveway mods.

 

[runamuck]

seems like the 2500's should offer more options for gearing. that 6.4 is not that much more powerful than the 5.7 but the truck weighs at least a thousand # more. they should start out at 3.92 and offer 4.10/4.30/4.56 for 95$ like they do the 3.92 I got in my 1500

 

[Pull Ya]

If your ever going to go to a bigger tire I think the 4.56's are going to be a must have.
Jay

 

[RoadRamblerNJ]

seems like the 2500's should offer more options for gearing. that 6.4 is not that much more powerful than the 5.7 but the truck weighs at least a thousand # more. they should start out at 3.92 and offer 4.10/4.30/4.56 for 95$ like they do the 3.92 I got in my 1500

The HD's offer taller gears like 3.73s and I believe one even taller (3.21 maybe) for tow vehicles doing lots of highway miles.

3.92s are only offered in 1500 trucks. HDs go right to 4.10s. That's it.

Small incremental jumps like 3.73 - 3.92 - 4.10 - 4.30 - 4.56 - 4.88 are too close together to really feel and measure. If the trans and engines are programmed correctly (they're not), you would only need maybe 3 different ratios to provide a usable combination. Remember, there are far less HD trucks sold than light duty trucks.
As for truck weight, horse power, torque, well, HD trucks have HD radiators, trans coolers, massive rears and underpinnings. The 392 motor was de-tuned specifically designed for longevity. That's why the 392 in a Charger/Challenger make so much more hp. Very few internals are interchangable.
The HD trucks can leisurely pull a large boat while a 1500 is huffin' & puffin'. Nobody ever said you need massive hp or lbs. ft. of torque.

If that ain't enough grunt, you need an oil burner. And a thicker wallet.

 

[AFMoulton]

The HD's offer taller gears like 3.73s and I believe one even taller (3.21 maybe) for tow vehicles doing lots of highway miles.

3.92s are only offered in 1500 trucks. HDs go right to 4.10s. That's it.

Small incremental jumps like 3.73 - 3.92 - 4.10 - 4.30 - 4.56 - 4.88 are too close together to really feel and measure. If the trans and engines are programmed correctly (they're not), you would only need maybe 3 different ratios to provide a usable combination. Remember, there are far less HD trucks sold than light duty trucks.
As for truck weight, horse power, torque, well, HD trucks have HD radiators, trans coolers, massive rears and underpinnings. The 392 motor was de-tuned specifically designed for longevity. That's why the 392 in a Charger/Challenger make so much more hp. Very few internals are interchangable.
The HD trucks can leisurely pull a large boat while a 1500 is huffin' & puffin'. Nobody ever said you need massive hp or lbs. ft. of torque.

If that ain't enough grunt, you need an oil burner. And a thicker wallet.

Or some forced air induction


2018 2500 6.4 4x4 4.10 Amsoil SS 0w-40, Softopper
Black Rhino Arsenal 18x9 +12mm
Cooper St MAXX LT295/70R18

2016 Durango 5.7 AWD 3.07 Redline 5W-30 RP 10-48
1996 Nissan Altima 2.4 Amsoil SS 5W-30

 

[Tumbleweed]

Want to start personalizing the truck a bit with simple driveway mods.

You do realize that swapping gears is NOT a simple driveway mod, correct? Special tools, dial indicator-housing spreader-dummy bearings-gear paint etc., are required. Experience is a huge plus. And yes if 4x4 then you will need to do both axles.

 

[Jayco]

I do realize the scope of work required, that’s not the issue.
I ordered a HD with a 3:73 and should have gone with the 4:10.
But I also want to stay inside my warranty.
I don’t drive the truck much. Mostly to pull my 9000 pound travel trailer (fully loaded truck bed and trailer) about 8 times a year. Have had the truck 1 year and mileage is barely over 5K. I just want to go now when I want to go. And I want to go up highway hills without issues.
All I’m saying is I’d like just a little more
No. Burning oil is not an option.

 

[runamuck]

I have been thinking of going with an hd but the 15 more hp and 18 more # of torque from the 6.4l seems to me would be cancelled out by the 1000# more empty wt. of the truck so 3.73 gears would be kinda high. 4.10 the better choice of the two available options. maybe should offer 3.92 and 4.30. people say the hd tows fine, just hard to convince me due to the numbers. diesel not an option for me.

 

[Graygoose]

3.73 to 4.10 isn't that much difference, if you do the swap, agree with most, at least go 4.56's

 

[Nickx86]

4.56 will probably net you better overall driving in stock tires, 35 I ha be heard are ok w 4.56 but maybe 4.88. These trans gearing are meant for the oil burner, Hemi loves the deeper gears