yeah, I know, it's not a jeep. But instead of joining a dodge forum for this question I thought I'd try it here.
The 8 1/4 rear axle needs a new shaft. It has a bow to it, resulting in about 1/4 inch runout at the flange. my guess PO hit a curb, or a deep chuckhole.

Seems that in 2007, there was an upgrade to these shafts. So there is 2 choices to make; The QUITE expensive 'small' axle which I have (about 300 bucks) or the larger axle for basically late 2007 and up... for about 110 bucks.

So of course, the bearing is different. the larger bearing, for the larger axle actually has a SMALLER OD ( .005 inch smaller) than the bearing residing in the tube now.

Am I doomed to having to get the more expensive, lighter axle just so the bearing is the same... or can the axle tube accept the smaller OD'd bearing of the heavier/cheaper to buy axle shaft?

I guess another way to ask this is did mother Chrysler use the same axle housing for both the heavy or light axle shafts, and it's just a matter of putting the correct bearing with the appropriate shaft?

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2006 KJ CRD, bought 9/11/14, 70,500 miles. Circulating Rotella T6 5w-40
11-3-14 oem stat installed
11-5-14 gen II FH installed.
Sasquatch elbow kit, samcos, GDE eco FT. 11-26-14
80,500 miles, engine is disassembled, awaiting parts 3/18
Budget?? Sure! 'Everything I have'.
New "Pet" name for My Jeep; 'Soul Sucker'

Have you compared the OEM housing part numbers between the two different models?
You can do that here:> https://www.factorychryslerparts.com/
If the OD of the bearings are different, then I suspect the housing are different.

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Supporting Vendor and Moderator of LOST
05 Jeep Liberty CRD Limited
Ironman Springs/Bilstein/Shocks
Yeti StgIV Hot Tune
Week's BatteryTray
No FCV/EGR
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Carter Intank-pmp
2mic.Sec.Fuel Filter
Flowmaster/NO CAT
V6Airbox/noVH
GM11 Bld.fan/HDClutch
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98 Dodge Cummins 24 Valve

Good idea. Headed there right now!
Yeah, Son ordered the cheaper axle last week, and it showed up today.. Considerably heavier than the one it 'may' replace!

Edit to add;
so, that was a lonnngggg rabbit trail to follow.
Looks like Sonny got on some 'parts house' page, which I confirmed 'RockAuto' shows 2 different axles. One with 41.1 mm journal, the other is 43.3 mm journal. No reference to what option would have either.
The respective bearings only differ by .005 inch on the OD.
According to the link you sent me, I cannot find any reference to the larger 43.3mm axles. anywhere.
They DO however, show the 2 different bearings, and seals!!! Clicking on THOSE individual parts both show those 2 sizes fit 2007 and up Nitro. Why would they show 2 sizes of bearings, but only one size of axle shaft?!?
Spline, Overall length, all are identical on these shafts, it's the major diameter and length of that first 'step' is longer down the shaft.

As far as checking the housing #... they only show one 'complete assembly'. No reference to what axle shaft, bearing, or seal it's equipped with. Only if my axle housing has a certain 'tag' would the replacement fit. I imagine it's a certain gear ratio and type of differential. Hey, it's 13 yrs. old, and not all variations are probably available anymore!!
Looks like we'll have to hunt down a 41.1mm shaft. Nitro brand axles show one for $230, but I have to snag the tone ring off my original shaft

_________________
2006 KJ CRD, bought 9/11/14, 70,500 miles. Circulating Rotella T6 5w-40
11-3-14 oem stat installed
11-5-14 gen II FH installed.
Sasquatch elbow kit, samcos, GDE eco FT. 11-26-14
80,500 miles, engine is disassembled, awaiting parts 3/18
Budget?? Sure! 'Everything I have'.
New "Pet" name for My Jeep; 'Soul Sucker'