JTDR with 373 Conversion to 488: Requires Entire Front Axle Changeout

[MOPAR Boy]

So, I’m going to be changing out the stock Falken 33 MT’s on my soon to arrive 2021 JTDR to 37X12.50R17 shoes, and have my dealer install the 2 inch Mopar lift kit. I also plan to immediately change out the OEM mandatory stock 373 gearing (that is the only option on the JTDR) to 488 to accomodate the 37’s.

My dealer says I absolutely cannot do this gear change with just the Mopar JPP 488 re-gear kit for the OEM stock front Rubicon M210 wide axle, because the OEM differential case on the factory equipped Dana 44 M210 373 Rubi is just too small. Therefore, he says that re-gearing from 373 to 488 will require that the JPP Ultra Dana 44 M210 wide crate axle, equipped with 488 gears, will be necessary to replace the OEM front axle (equipped with 373 gearing). However, he says my stock OEM 373 rear Dana 44 M220 wide axle will, in fact, accommodate the 488 re-gearing, without requiring an entire crate axle swap-out, because its differential case is large enough to accomodate the 488 re-gear.

BTW, I will use all Mopar parts (purchased from the dealer), and their shop labor to install everything (including the Mopar lift kit) to keep my warranty fully intact.

Has anyone had any experience in such a conversion from 373 to 488 on a diesel Rubi Gladiator, who can offer any help/advice/pointers on this project?

Thanks!

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[rharr]

all the axle housings are the same on the rubies. Gas guys fit 4.88's all the time therefore they should fit on the EcoD.

 

[MOPAR Boy]

I may be wrong, but I believe gas Rubis are OEM 410, which is not 373.

 

[Basicjon]

I may be wrong, but I believe gas Rubis are OEM 410, which is not 373.

I’m not the smartest person but it sounds like they’re trying to make money off of you

 

[FitfulGoat]

I may be wrong, but I believe gas Rubis are OEM 410, which is not 373.

This is true but the axle housing should be identical. They both use the same wide Dana 44. I don’t see them using different size axle housings for the different gearing…

just looked at mopar parts online and the part number for the front axle assembly shows the same for rubicon diesel and rubicon gas.

 

[JTPatriot]

"IF" anything needs to be changed it would be the carrier. I am not sure where the break is on what size carrier is used. It may be 373 or 410. It will allow lower (higher numerical) gearing. The axle is the same as is on my gasser that had 410's in it and I went to 4.88's no problem. Maybe someone else knows where that break is at for sure. No matter what the axle is fine, only the carrier is in question.

Found this on west coast differential.com
It is saying 3.07 as the break.

 

[FitfulGoat]

"IF" anything needs to be changed it would be the carrier. I am not sure where the break is on what size carrier is used. It may be 373 or 410. It will allow lower (higher numerical) gearing. The axle is the same as is on my gasser that had 410's in it and I went to 4.88's no problem. Maybe someone else knows where that break is at for sure. No matter what the axle is fine, only the carrier is in question.

Exactly, changing the carrier should not equal changing out your axle assembly. The same differential housing should accept a larger carrier for the increased gearing.

 

[Kevin_D]

Isn't 4.88 a bit extreme with the diesel?

Kevin

 

[JTPatriot]

Exactly, changing the carrier should not equal changing out your axle assembly. The same differential housing should accept a larger carrier for the increased gearing.

Not nit picking here but the carrier does not change size. it moves the mounting flange of the ring gear either closer or farther away from the center line of the pinon. In this case, if a carrier would be needed it would move the ring gear closer from the center line of the pinon as the ring gear would be thicker. If memory serves me correct.
But with the added information I added to my last post from West Coast differential it does not need a change.

 

[MOPAR Boy]

But, we must compare apples to apples. I’m referring to the NEW 2018 and up Dana 44 Ultra M210 wide front axle, diesel, Rubicon, Gladiator. Pre-2018 axles could be a different story.

 

[FitfulGoat]

Not nit picking here but the carrier does not change size. it moves the mounting flange of the ring gear either closer or farther away from the center line of the pinon. In this case, if a carrier would be needed it would move the ring gear away from the center line of the pinon as the ring gear would be thicker. If memory serves me correct.
But with the added information I added to my last post from West Coast differential it does not need a change.

Yes, to be perfectly correct you should adjust your deck height by getting a different carrier to accommodate for the changes in gearing and the overall thickness in the ring gear. Not just “change your carrier”

overall the message here is the same

 

[FitfulGoat]

But, we must compare apples to apples. I’m referring to the NEW 2018 and up Dana 44 Ultra M210 wide front axle, diesel, Rubicon, Gladiator. Pre-2018 axles could be a different story.

All gladiator rubicon’s came with the same ultra wide Dana 44. The only difference is the gearing and possibly deck height on your carrier to accommodate the specific gearing.

 

[JTPatriot]

All gladiator rubicon’s came with the same ultra wide Dana 44. The only difference is the gearing and possibly deck height on your carrier to accommodate the specific gearing.

What he said

 

[LostWoods]

For the same reason dealerships don't typically replace just gears for warranty, full axle replacements are significantly less labor and have a substantially lower return rate. They probably don't want to do gears because there is a ton more liability that goes with it.

I suggest finding a reputable, local off road shop and having them do it because everyone here is right - the JTR has identical axle housings and carriers regardless of engine.

 

[LordEnzo]

Isn't 4.88 a bit extreme with the diesel?

Kevin

It would be. Gassers go 4.88 due to the lesser torque and it being a Lil higher on the curve. But even then, most don't need the research until ur up in elevation. I'm running 37s on my gasser with no research, at sea level, and extra weight in rear due to upper Decker and winch. I do just fine, on road and in sand/mud (FL swamp nastiness). Sure, I noticed a small loss in overall power, but I can still pass on highway and get out of all the sticky situations I been in.

All that said, most (if not all) the diesels have shown to have enough torque where needed to move 37s better than gassers, without regearing. If u absolutely must research, I would suggest just bumping to 4.10s. This should help accommodate for any extra weight added on aside from wheels/tires/suspension. This is what i plan on doing when I trade in for the diesel as I plan to run 38-40s.

Now, if u plan on going hard core off road, the general consensus is the the oe d44 supports up to 37s. So u would need to beef up ur oe housings, or swap out to to the 44/60 advanteks posted earlier (pending how hard-core u intend to go). Occasionally seeing the trails tho, u should be fine.

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