I have a 2016 Ram 2WD with ECO Diesel and have a 3.55 rear end ratio that I'm considering having changed. Just curious if any of you with these newer Rams have gone through this and what you ended up paying for labor.

- EM

Buy one out of a junk yard.

I would make sure you don't go to low with your gear selection,

Are 3.91 the factory option on the EcoDiesel? Is the transmission gearing identical between the factory rear gear options.

I recall Bosch engineers mentioning keeping rpm below 3k to insure fuel pump longevity.

Red

I have changed gears in 4x4 when I put larger tires on. I did the swap myself front and back so I only paid for the gears and carrier for the front.

I would not suggest changing them on your truck because if you do then I bet it would be worse and would not be a eco diesel anymore. Not worth it IMO.

I have 3.55s now and with the factory 20" wheels, the effective ratio is affected more than I would prefer. The 3.91 ratio is an option but I was not aware of that when I got my truck. I could only see 3.55s as an option over the 3.23 standard set. I am looking at a 4.10 OEM gear set that with my 20 wheels should have me closer to the factory 3.91 ratio. So, not looking to go crazy or beyond what the factory does already. My question pertains to anyone that has done this with a dealer and what they charge. I need to stay in warranty.

- EM

You would have to check with your dealer however with retail dealership pricing I would expect it to be at least $1500.

Sheldon

Agreed Sheldon. I have done that yet but will be. I have found new OEM 4.10 gear sets for $400 and 3.92s for $300 which has to be far less than through a dealer. But, I'm sure they don't like people coming in with their own parts. I just need their labor due to the factory warranty.

- EM

With the speedometer signal being sent electronically, how exactly do you compensate for a change in axle ratio? Do you have to take it to someone that can reflash the signal? I realize that it isn't as simple as changing a speedometer pinion gear like we used to do.

Most likely a re-flash of the computer would be required. Around $1,500 sounds about right.

Probably best to ask the dealer.

What axle in the eco diesel? Is it a rear diff mounted speed sensor like just about all the other dodge trucks?

If so, a gear ratio change won't effect speedo calibration because the tone ring doesn't care about gear ratio. It rotates with the ring gear and the tires, so it makes the same number of revolutions per mile.

That said; changing tire size WILL alter speedo calibration because now the tone ring for the speed sensor on the ring gear no longer has the same rev/mile.

This can be reprogrammed with a dealership diagnostic scan tool. Not your generic part store code reader. I have a snap on MT2500 that I recalibrated the soeedo in my Dakota with.

The snap on versus, solus, and modus scanners will work too when they have software loaded that's current for your model year truck. FYI the speedo calibration is done through the anti-lock brake controller, not the main engine computer, which is why a generic emissions code reader don't work. (It's still connected through the obd-2 port under the dash though)

fyi.... we haven't been able to "recalibrate" speedo's on vehicles for about three years at the dealer. They've also taken away adjusting the tire psi threshold so if you change to a larger show pony tire that can be run at a lesser psi than a factory tire (think 2500+ with lift etc...) you get to live with the low tire psi warning.

That seems ridiculous. The factory took away that adjustability in the software? Why would they do that? Have the dealers all cried foul back to the factory? More reasons why my 06 5.9 cummins will be the last truck I ever buy, as long as I can keep it from rusting away or getting wrecked

you can thank the EPA for that.... I'm sure corporate couldn't have given a hang over it.