AMC CJ Axle Swaps
I have been working on this page, learning new things as I go - I have learned a significant amount in regards to D44 front swaps, and other lighter duty swaps.  Feel free to use this page to get some ideas and thoughts, but I urge anyone that takes on a project of this type to learn as much as possible from  various sources before starting.
-Mel

Why do an axle swap?
There are many reasons why people decide to do an axle swap  the most popular being:
1. They are upgrading to large tires (usually the threshold is 35" or bigger) and need added strength
2. Along the same line, they may be adding horsepower (i.e. a engine swap or performance upgrade) and need the added strength
3. They would like a wider axle for greater stability when lifting their Jeep either via a Spring-over or Spring-under lift.
4. Their old axle took a turn for the worse & they decided why not put in something stronger

Are my current axles strong enough?
Front End:
All AMC era CJ's came with the Dana 30 front axle.  In the late 70's (I believe it was '77 or '78) they made the switch from drum brakes to disc brakes.  This axle seems to do fine on tire sizes up to 33", with stock engines.  When you put additional stress on the axle via a front locker, more horsepower, larger tires, these axles may break.  The most vulnerable part is the U-joint.  Warn and Superior produce an upgrade kit which includes high strength shafts, and converts the U-joint to the stronger 297X unit.   However, this upgrade will run you $500 and higher, and if you break one of these shafts, you have an expensive replacement.  Overall, it is up to your personal preference what to do, installing the upgrade shafts is much easier than an axle swap, but you still have the smaller ring gear, brakes and knuckles of the Dana 30 on your rig.  

Rear End:
Dana 44 in CJ5's
CJ5's up to 1976 came with a Dana 44 rear end.  Considering that a Dana 44 (in general) is a popular swap to go to in the rear of the CJ's it has been my experience that most people believe these will hold up pretty well to tire sizes up to 35".  From what I have seen, most hardcore Jeepers upgrade this axle if they are running larger tires.  Besides, this is a "narrow-track" axle and to get 35" tires or higher means a pretty sizeable lift, and this means tippy-tippy of your CJ.  So, this is another reason why it is popular to swap these axles.
AMC 20 
This axle came in two widths - from '76-'81 it came as a "narrow-track".  This is the same width as the CJ5 Dana 44.  From '82 to '86 it was 4" wider (approx.)  For about $300 you can get a one-piece axle upgrade from Superior, Moser or others that will make this a much stronger unit.  There is actually some debate that it is as strong as a Dana 44 following this upgrade (I think it makes it strong, but not as strong as a Dana 44).  Anyway....   you can make your own decision.  As with the CJ5 Dana 44 most hardcore Jeepers upgrade when going higher than 35" tires, even if they have put the one-piece kit in (which, should be one of the first things you do to your CJ if you are planning to keep your AMC20).  Keep in mind the tippy-tippy statement from above, it holds the same for the narrow-track AMC 20.  

Added considerations
There are other things to consider the biggest being the type of Jeepin' you'll be doing.  If you are going to be doing a lot of Jeepin' that involves mud, dirt, and places where the ground is soft, and/or you get a lot of wheel slip, then you may not have as much torque stress on your components.  Now, if you are going to be doing rockcrawling, there will be a huge amount of torque and stress on your components when trying to power your rig up the face of a boulder.  
Also keep in mind the kind of locker you may be running (if you are) - a lightweight locker such as a lock-right may break before some of your other components.  Heavyweight lockers such as a Detroit or ARB may cause added stress on your axle.  And vice-versa, if you swap in a Dana 60, the lightweight lock-right will be a weaker link than other Dana 60 components.


What axle can I swap under my Jeep?
Here is a link to an excellent site that lists the track width of various Jeep Vehicles:
CLICK HERE

The most important things to keep in mind are
1. For the front, you need a differential that is off-set to the passenger side
2. For the rear, you will need a differential that is centered - with the exception of Jeeps equipped with "quadratrac" which is offset to the passenger side

The most popular front axle candidates are:
Dana 44 from Wagoneer 1975-1979
Dana 44 from Scout II 1975-1980
Dana 44 from Chevy Blazer or truck
Dana 60 from variety of trucks

The most popular rear axle candidates are:
Heavy-Duty AMC 20 from a Wagoneer 1980-1986
Dana 44 from a Grand Wagoneer 1987-1991
Dana 44 from a Scout II
Dana 60 from a variety of trucks
Chevy 14 bolt
Ford 9"
Ford 8.8" from an explorer with disc brakes

What are the considerations when choosing an axle:
First off - decide weather you are going to do a heavy-duty (i.e. Dana 60's/14 bolt) or medium duty upgrade (i.e. Dana 44, Ford 9", Ford 8.8").  That is dependent on the same factors listed above for doing the upgrade in the first place (mainly tire size & horsepower).  Also keep in mind that a bigger axle means a bigger differential housing and less ground clearance.  So, everythings a tradeoff, you can put a set of Dana 60's in and pretty much guarantee that you won't break anything, but you will be peeved when you hang up on that rock that your buddy's CJ got over with his Dana 44's.

You also must consider axle width & your states inspection requirements.  If you don't "cut down" the axle and run it full-width will you be street-legal, and do you care?  Most people do.  There are several aftermarket companies that produce fender flares that will help you out, but they won't cover a full-width Dana 60 axle.  

Also keep in mind the bolt pattern.  If you are doing a front-swap only, there is a chance you can change to a 5 bolt on a Dana 44.  If you are doing a rear swap, you pretty much have to stick with what is on there.  There are a few 5-bolt rear axles out there (i.e. J-series truck axles from the late 60's early 70's).  A lot of folks just get a matching set & run 6-bolt or 8-bolt anyway.

How much does the axle cost:
The price varies from place to place.  Obviously the more plentiful and the older they are, the cheaper they are.  Chevy Dana 44 axles can be relatively cheap & may be had for less than $100.  However, axles like a '87-'91 Wagoneer rear axle may run you $300 or higher, or a Ford explorer axle may run you $500 or higher!

 Can I "mail-order" an axle?:
Sure!  There are plenty of places that will make your life simpler and make you up an axle ready to go with cool things like gears and lockers already in the diff!  Be prepared to pay though.  Anywhere from $1200-$5000 per axle, depending on your options.  Some of the places for these axles are:  Currie, Dynatrac, Sam's off-road, OK 4wd, Tri-County Gear.  Dynatrac uses all new (even new housings) components - but you PAY BIG for this privilege.  Currie and others refresh used housings.   

VARIOUS AXLE QUICK OVERVIEWS:
'75-'79 Front Dana 44 Wagoneer Axles:
Wagoneer axles are very popular conversions.  There are two ways you can go about this, you can cut the long side of the axle down by about 4" and make it wide-track CJ width (For details on this CLICK HERE), or you can leave it the stock size and "outboard" your spring hangars. (For pix of outboarded springs CLICK HERE).  Very important, is to notice my chart above (CLICK HERE) that lists widths - there was a "wide-track" Cherokee axle at the same time, that is wider than Wagoneer axle.  Keep in mind, that if you don't cut the axle down, the tires will stick out farther (duh).   

'75-'79 Front Dana 44 Scout II Axles:
These are also very popular, but the thing to watch out with these are the caster and the fact that the "outers" of these axles are basically a Dana 30.  With this swap you will either need to reset the caster, or cut the axle down & reset the caster while you are doing that (For details on this swap CLICK HERE).  

To cut, or not to cut THAT is the question ALL OTHER AXLES:
Sorry to get lazy at this point of the show here, but basically axle swapping with everything else comes down to the main question "Do I want/care to have this axle be stock, or close to stock width" 

If you answered "Yes" then you will have to cut down both sides of the housing.  Now - for a quick overview of what this involves, check out the link  for the Wagoneer axle - John Nutter did a nice write-up about how he cut down a Waggy axle.  However, with a waggy or scout axle, you only need to cut the one side.  Most others you will need to cut both, which adds to the cost.  You can send your shafts away to Moser and for about $60 each (shaft) they will respline them for you for the new length.  Most shops will charge you $125-$200 per side when cutting & resetting a tube.  Just FYI - check around.

If you answered "No" then you will just need to relocate your spring pads and, on some axles, outboard the spring hangars (see link above).

Other considerations:
Well, many truck axles are set up for spring-over, and this is especially true of Chevy 44 front axles, which have the spring-over perch molded into the side of the diff housing on the passenger side.  What does this mean to you?  This means that if you want to go spring-under with that axle you will need to grind into the housing to make a nice spot for your perch.  This is true, but opposite with the Wagoneer axle, if you want to go spring-over you will need to grind into the diff to make a nice spot for the spring perch on top.