YJ Wrangler SOA with FSJ Wagoneer Axles

This is for Jeep Wrangler (YJ) from 1985 to 1995 that wish to upgrade to the Full Size Jeep
NT Wagoneer or Cherokee axles. These will come from 1980 to 1983 NT Cherokees and
1980 to 1991 Wagoneers and Grand Wagoneers, most folks will want to avoid the 83-84
vacuum disconnect front axles but they are useable, just a bit harder to work with.
If you are swapping to a passenger drop transfer case then the 74 to 79 front axles are
what you want, most of the 74-79 rear axles are too far offset to be of any use.

There are many writeups on how this is done so I will not go into a lot of tech here
but lets talk about some numbers.

Lift Gained:
The basic math with using my front SOA perches is 4 3/4" plus the thickness of your
existing spring packs, if you change springs that math also changes. The rear perches I
make are cut low, you may need a small block to level out the rear but it's easier to level
the rear up than it is to lower the front down.

Front Perch Spacing:
YJ front spring perch spacing is 31" on center, FSJ front perch spacing is 32" on center.
So you are 1/2" off on each side, there are a couple of ways to deal with this.
1. Ignore it, you will still get the axle to bolt in, you will however eat through bushings.
2. Use offset front spring shackles, these are pricey.
3. Outboard your front spring hangers 1/2" on each side, this is really a pain to do.
4. Move the front SOA perches in, it's hard to get the full 1/2 on the diff side without
making the perch welding difficult but 3/8" is not bad, you have to grind new slots
for the ubolts on the diff side anyway and you are already grinding the upper area
so this is a fair comprimise, you will still be 1/8" off, but you will never notice this.

Rear Perch Spacing:
YJ rear perch spacing is 41.5", FSJ NT rear perch spacing is 44", this is really a no brainer
you are 1.25" too wide per side, so besides putting perches up top you are moving them in.
You can try removing the FSJ rear perches and moving them in (those axles
come SOA), my luck has typically been 50/50 on this, one comes off easy,
one gets destroyed. If you are using my front SOA perches (7" long anti-wrap)
and do reuse the FSJ rear perches (3 3/4" long) you will have different spring
compression rates, you may or may not be happy with this.

Front Pinion Angle and Caster:
FSJ front axles come with the front caster set between -3 and -6 degrees, if you
rotate the pinion up for a better driveshaft angle you want to keep a minimum of
-3* to maintain decent road manners, anything less and you will get into a "cut
and turn", it's labor intensive but not terribly technical, there a lot of writeups
out there on this from the IH and Binder folks, they were blessed with 0* of
caster and pretty much have to do this every time they SOA.

Rear Pinion Angle:
Set it for what ever pinion angle suits your build, there is no caster to deal with
here, you should however follow the rules for proper driveline geometry which
varies depending on what type of driveshaft setup you plan on using.

Steering Correction:
All the same rules that apply to FSJ and IH front SOA conversions apply here too.
You are going to need at least cross-over steering or full high-steering.
Please read this document.

Other Stuff:
With any lift some things have to change, brake lines and shocks get longer,
driveshafts get longer and may even need to upgraded to higher angle yokes,
some exhaust components may need to be moved and emergency brake
cables may need to be made longer. My advise to you is that when you go
looking for your FSJ axles get the ebrake cables and the spring plates, you
will need new ubolts, those sizes and part numbers are listed on the main page.
You can also buy them here.

FSJ Axles:
The front axles on all 74-91 FSJ are D44 low pinion axles, this never changes.
From 80-85 the rear was the M21 or what folks call the AMC20, don't confuse
this with the AMC 20 found in CJ's that are two-piece, these are solid one-piece
axles and the have a "slighlty" larger pinion that a D44, strength wise they are equals.
From 86-91 FSJ's used the D44 in the rear.

That's a nice tease video but lets look at what took place before that.

The tube side perch is pretty easy to weld into position.

The diff side perch is a tighter area to weld.

Grooves for the ubolts must be cut into the housing.
This is really the hardest part.

Bolted in, the spring plates needed to be notched to clear the shocks.

Cross-over steering is mocked up.
Notice the need to use the spacer to clear the spring, this can be avoided
by using the raised steering arm linked in the SOA document above.