Axle ratio?
 

Pretty sure I have 3.73's. How can I tell from the VIN? Tried some free VIN check sites, but mostly just general info.
Thanks

Use the vin decoder on this site. It is in the menu bar at the top of the page under tools. Once you have entered your vin look under the Equipment tab. It should be the first thing listed.

If your under 2k rpm at 70 mph you have them

If you have a 13+ and a 2500 you have 3.42
We need your year and 2500/3500. If it's a 10-12 then it can be a 3.73.

I did this, and the first line had 3.73 Axle Ratio with a green check mark. This must have been a special order?

Most trucks prior 2013 came with the 3.73's.

Yeah, I knew that. Most HD diesel pickups from all 3 makes used to have 3.73 gears. thought the new ones came standard with 3.42's. That's why I'm wondering if this is correct

2013 and up 2500 is only 3.42, it's been a heavily discussed issue on the net. Even vin decoders and window stickers may even list 3.73/4.10 but somewhere else on the sheet it will list 3.42.
Long story short 2013+ 2500 is a 3.42 unless you regear yourself.

Be sure and fill out your signature so we're not guessing what you have :)

Yep, 3.42's are all you can get in a 2500 Cummins. Not sure why FCA went that way. Most will use these pickups for towing, and in mountains a lower gear ratio would be better. Also if you go to bigger tires.
For a minuscule improvement in fuel mileage when running unloaded?

Yes and when you can still pull off an over 17k tow rating why not. Don't get me wrong I believe you should be able to order whatever rear you want, but I guess they figure if they can max you out with the 3.42 no need for the 3.73 or 4.10 in a 2500

Absolutely correct RyeThomas. You can still tow 17K, but you can pull it more efficiently with lower gears.
Thank you for your service.

Go to this web site.
Under "equipment listing" you type in you VIN#
You get a "build sheet" of how you truck came from the factory which list gear ratio.
https://www.dodge.com/webselfservice/dodge/

I had a '93 dodge with 3.55 gears and now an '04 with 3.73 gears

Both trucks do/did 2000rpm at 110kmh

Tire size was the difference. slightly larger diameter tire on the '04




I'm guessing they are manipulating gear sets to hit a target RPM with a certain tire package....