2019 Dodge Ram 1500 Axle Ratio Update after PCM Tune

[bmagnan]

Hello,

I have what I hope is an easy question that I can't seem to get a straight answer for.

I have a 2019 Ram 1500 with the 5.7L engine and I had an MDS disable tune installed a few months ago. Simply put the best money I have spent on my truck so far!

When the tune was created I had 3.21 gears in the truck, and now I want to install 3.92 gears. My tuner is remote, and I don't have HP Tuners... so I can't modify the PCM tune that was installed. I do have AlfaODB and I can update the axle ratio setting in the BCM... but I'm curious whether or not the PCM will see this new value and use it, or if I need to send in the PCM tune for an update.

So simply put, I'm wondering if anyone out there has changed axle ratios after installing an engine tune, and if so, did you ever go back in and update the engine tune or did you only change the axle ratio in the BCM.

HP Tuners support said this:
With our gear and tire wizard in the VCM Scanner, you can make the BCM change in the controls and special functions. Changes will then need to be made to the tune file in the VCM editor to accommodate the new gear ratio

To me that seems to point to a change also needed in the engine tune... but I don't understand why it would be needed.

[LilSick]

HP Tuners support said this:
With our gear and tire wizard in the VCM Scanner, you can make the BCM change in the controls and special functions. Changes will then need to be made to the tune file in the VCM editor to accommodate the new gear ratio

To me that seems to point to a change also needed in the engine tune... but I don't understand why it would be needed.

first of all without a dongle how to they expect you to use their scanner?

and i did not change anything in my trans or engine tune when going from 3.1 to 3.7


i just went into the bcm and wiped out my adaptive cruise control.
hope yer truck does not have that.
does it?
if the trucks are like the cars its not gonna have it any more : )
these guys are not huge mopar fans

[bmagnan]

I was planning on making the changes in the BCM with AlfaODB for the axle ratio. From what I can figure out, HP Tuners only sets the change in the BCM, which is why some folks get the ACC/FCW errors. It seems like you would need to do the gear ratio change to both the PCM (using VCM Editor) and the BCM (using VCM Scanner) to make things work right (which might be what Diablo does).

What vehicle did you swap gears on? Interesting that things just worked fine for you.

[LilSick]

16 scat

i dont know if i would describe it as everything fine

ditched the acc and it shifts right

on the street or at the track

speedo is accurate now too

took a bunch of messing with it

[vndetta79]

I did a 3.21 to 3.92 swap in my 19 Ram and just used AlfaOBD. Didn't change anything in the tune when I did it. I find AlfaOBD better for ratio changes and gas tank capacity changes. The only tune changes I made (eventually) were the shift points to better suit the gear swap.

[bmagnan]

Was that a 19 classic or the 5th Gen?

How did you like the new ratio?

[vndetta79]

5th Gen