Determining rear axle equipment?

[Emittim3]

I'm a recently re-new to Ram owner. Bought a slightly used '23 2500 Cummins.

I was a proud owner of a 2nd Gen 2500 Cummins in the late 90s and early 2ks, hauling rock crawler Jeeps all over the CO mountains.

Anyhow, my '23 is a wonderful upgrade from memories I had of my old 2nd Gen, and a great upgrade from my Ford Excursion 6.0.

One thing I've noticed, is it feels like there is a locker (or limited grip .. err slip) in the rear axle at times. I've looked for VIN mappings and have crawled under to see if there was a tag bolted to the cover but I haven't found anything yet to tell me what gear ratio, or other equipment is in the diff.

Is there a way to tell what is in my rig 11.5 rear axle without pulling the cap off? It's not due for a diff oil change just yet...

 

[rzr6-4]

Vin lookup

Search your VIN there and you should be able to see your gear ratio.

90% sure the 2500s still use a torsional diff, at least they did when mine was made. Slow/low load it will behave similar to an open diff but when you get on it, it will transfer some of that tq to the other side.

How torsion diffs work

 

[06 Dodge]

I'm a recently re-new to Ram owner. Bought a slightly used '23 2500 Cummins.

I was a proud owner of a 2nd Gen 2500 Cummins in the late 90s and early 2ks, hauling rock crawler Jeeps all over the CO mountains.

Anyhow, my '23 is a wonderful upgrade from memories I had of my old 2nd Gen, and a great upgrade from my Ford Excursion 6.0.

One thing I've noticed, is it feels like there is a locker (or limited grip .. err slip) in the rear axle at times. I've looked for VIN mappings and have crawled under to see if there was a tag bolted to the cover but I haven't found anything yet to tell me what gear ratio, or other equipment is in the diff.

Is there a way to tell what is in my rig 11.5 rear axle without pulling the cap off? It's not due for a diff oil change just yet...

You most likely have 3.73 gears that was the stock gear until 2025 then it went to 3.42, but ordering dealer could have ordered it with 4.10 so its best to look up your build sheet based on your VIN number to be 100% sure...

 

[Emittim3]

Hmmm. Vin lookup is vague at best.

"ANTI-SPIN DIFFERENTIAL REAR AXLE"

No mention on gear ratio.

 

[RamDiver]

Hmmm. Vin lookup is vague at best.

"ANTI-SPIN DIFFERENTIAL REAR AXLE"

No mention on gear ratio.

Try the window sticker.

https://fcagroup.my.site.com/RAM/s/equipment-listing
All caps for VIN

Here's another.

Window Sticker Lookup by VIN

Use your VIN number to get your Buick, Cadillac, Chevrolet, Chrysler, Dodge, FIAT, Genesis, GMC, Hyundai, Jeep, or RAM Window Sticker

windowstickerlookup.com

.

 

[Emittim3]

Try the window sticker.

https://fcagroup.my.site.com/RAM/s/equipment-listing
All caps for VIN

Here's another.

Window Sticker Lookup by VIN

Use your VIN number to get your Buick, Cadillac, Chevrolet, Chrysler, Dodge, FIAT, Genesis, GMC, Hyundai, Jeep, or RAM Window Sticker

windowstickerlookup.com

.

That got it! 3.73 gears as expected.

"ANTI-SPIN DIFFERENTIAL REAR AXLE"

Maybe that the torsional diff?

And I wonder if this:

"SUPPLEMENTAL HEATER"

Means a block heater? Haven't checked to see if I can locate a plug as of yet...

 

[BossHogg]

Hmmm. Vin lookup is vague at best.

"ANTI-SPIN DIFFERENTIAL REAR AXLE"

No mention on gear ratio.

The 2023 RAM towing chart shows the 3:73 axle ratio as the only available ratio for all configurations of the 2500 with the Cummins engine.

 

[crash68]

"SUPPLEMENTAL HEATER"

Means a block heater? Haven't checked to see if I can locate a plug as of yet...

All the Cummins should have the block heater installed on the engine, it's usually just the electrical cord that needs to be added. You can find the block heater on the passenger side of the engine sorta behind the oil filter.
The supplemental heater should be referring to the ones in the HVAC system, something that's is on the EcoDiesel and the Cummins trucks starting with the 2019 model year.

 

[WY-Dave]

look in the owner's manual and diesel supplement. For my '18 it has the torsen rear and no friction additive needed. If you have the clutch system it will say to add it

 

[Emittim3]

All the Cummins should have the block heater installed on the engine, it's usually just the electrical cord that needs to be added. You can find the block heater on the passenger side of the engine sorta behind the oil filter.
The supplemental heater should be referring to the ones in the HVAC system, something that's is on the EcoDiesel and the Cummins trucks starting with the 2019 model year.

Thanks for this, I located the heater just behind the oil filter as instructed and yep, no cord so I've ordered the OEM cord so I'll have that for future mountain overnight trips. Thanks for this!

 

[Emittim3]

look in the owner's manual and diesel supplement. For my '18 it has the torsen rear and no friction additive needed. If you have the clutch system it will say to add it

View attachment 564160

I'll check that when I have a moment. Thanks!
the way it behaves on a sharp up slope switchback definitely doesn't feel like a limited (clutch) slip diff, so most likely its torsen as many have alluded to.

 

[Tominator223]

Used to be a sticker on pass side rear axle facing cab. Tells ratio.

 

[star_deceiver]

The torsional diff went away in 2019. You have a simple plate style LSD.