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tech
Axle Swapping
So, you're considering an axle swap. Many folks do them,
even though they SEEM complicated. In reality, they are not
really hard at all - given you do some basic planning
before-hand and have the skills to tackle the work.
At that same endpoint, though, you'll enjoy the benefits
of knowing your rig can handle the bigger tires, increased
traction and tackle more difficult terrain without breaking.
Since there's custom work involved, you'll need welding
skills handy. You'll need to find the axles - which will
depend on your end goal and budget. You'll basically need to
rework the driveshafts and steering, but this isn't as hard
as it sound nowadays.
Some companies will ship you everything you need from
brackets to welding templates and complete axles built to
your specs. You're in for a big bill if you go that route -
thousands of dollars, easily, for the gear alone.
Folks choose axle swaps for a variety of reasons:
- Driving a 4 cyl nets you
much lower gearing than the 6 cyl guys enjoy
- The desire for a
specific gear ratio, though your current axles won't
accommodate the ring gear size
- Big tires (35" and
larger) will almost certainly need bigger, stronger
axles - or lots of spares
Whatever the reason, here's some
useful info on what's available, what it has and some basic
ideas to get you started:
The Goal -
Bigger Axles for a YJ
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Many people consider
swapping dual Dana 44 axles under their YJs (or TJs,
or Cherokees, etc.). The stock Dana 35C has a bad
rap for being a weakling with tires over 33", and
putting a locker in it with 33" tires is a recipe
for breakage. And while you're swapping, why not do
the front as well? You might also want super low
gears some day, and they may be lower than the
4.56's from the 4cyl rigs -- these were the lowest
possible in a YJ D30 without custom bits. In fact,
you'd probably like to avoid custom-made parts
anyway, just in case they need to replaced quickly. |
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General Axle
Info
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Vehicle:
Stock '87-95 YJ (front D30, rear D35C)
Bolt pattern: 5 on 4.5", same as TJ/XJ/MJ/ZJ
Width: 60.5" rear, similar front
Brakes: Front discs, rear drums (10" '87-89,
9" '90-95).
Spline count: 27 spline rear
Caster: 6-8 degrees for manual tranny, 7-9
degrees for automatic.
Other: Front pumpkin is on the drivers side.
Rear pumpkin & t-case output are offset 5/8" to
passenger side (right of center) |
Vehicle:
'87-89 Jeep XJ or MJ with the metric ton option
(front D30, rear D44, often packaged with the towing
option)
Bolt pattern: 5 on 4.5" -- same as stock D30
& D35 on a YJ/TJ/XJ/MJ/ZJ. Could this be redrilled
to 5 on 5.5" or 6 on 5.5" to match another D44 front
axle? Probably not, due to insufficient flange
material outside the stock studs
Width: 60.25" -- virtually identical to stock
YJ/TJ/XJ/MJ
Brakes: 10x2.5" drums, vs the 9" drums on a
late YJ
Spline count: 30
Other: An excellent choice if only swapping
the rear. Spring perches are different than a YJ,
but that's not an issue for my SOA setup. The pinion
is slightly (1/4") offset (to which side?), so you
can't use the same spare axle shaft for either side.
Pinion U-joint is the same size as a '94+ YJ/TJ
(Spicer 1330) but larger than an earlier YJ U-joint
(Spicer 1310). Pinion length seems identical to D35,
so no driveshaft length mods should be necessary. |
Vehicle:
'71-80 Scout II rear, '74-80 front
Bolt pattern: 5 on 5.5", which allows
wheel-swapping with any CJ if you need to borrow or
lend a spare.
Width: 58" front, 58.25" or 58.5" rear --
2-2.5" narrower than a YJ. That's not a big problem
in the rear (other than off-camber stability), but
it'll reduce turning radius up front. Less wheel
backspacing compensates for this.
Brakes: 11" rear drums. What size front? Rear
hard line junction is on opposite side of axle from
YJ. Front brake line fitting is larger than YJ
lines.
Spline count: 30
Caster: 0 degrees '71-79, 3 degrees in '80. A
YJ wants about 7 degrees, so you'd have to rotate
the knuckles on the axle tubes.
Other: Scout fronts have the diff very wide
on the passenger side. This involves grinding to
change the spring perch, and requires a t-case swap
on YJ's. Tie rod mounting holes need to be redrilled
closer to knuckles to regain a tight turning radius.
Both rear axle shafts are the same length,
necessitating only one spare, but the rear pinion is
still offset 1.25" to the right, which is about 5/8"
farther than the stock YJ. |
Vehicle:
'71-77 Ford Bronco (D44 front, Ford 9" rear)
Bolt pattern: 5 on 5.5" -- same as a CJ
Width: 58" rear, similar front.
Brakes: Front drums '71-75, 11" front discs
'76-77, 11" rear drums. How wide are the rear drums?
Spline count: 30-spline D44 front, 260 (small
style) U-joint, 28-spline 9" rear (31-spline
available in aftermarket)
Caster: ???
Other: Very stout combination, but the 9"
rear would give a hellish rear driveshaft angle on a
SOA YJ. The coil suspension mounts will need to be
removed from the front. The knuckle U-joint is the
smaller D30 variety, but can be enlarged by swapping
in F-150 shafts (long side must be shortened). Front
diff is 3-4" closer to center than the YJ D30, but
clearance with an SOA is fine. Diff is on driver
side, like YJ. Spring perch is not integrated into
the diff housing. Rear diff is centered, but pinion
is 1.5" to the right of center. Like Scouts, the
stock tie rod / knuckle mounting holes lose turning
radius. |
Vehicle:
'74-91 full-size Cherokees & Wagoneers (SJ's)
Bolt Pattern: 6 on 5.5" -- same as Chevy 1/2
ton and Toyota. Can the rears be redrilled to 5 on
5.5"? Converting a front D44 to 5 on 5.5" requires
switching to knuckles, spindles and brakes from a
'74-76 disc brake SJ or Chevy Dana 44 and hubs &
rotors from just about any year Ford pickup (ask for
'79 F-150 if buying new, and get bearings & seals
from the same Ford). To do Nutter's high-steering
swap, use '74-76 SJ knuckles as well. Pre-'74 SJ's
had 5 on 5.5" D44's, but with weak 2-piece shafts in
the rear and closed knuckles up front.
Width: Narrow track (Wagoneers, Grand
Wagoneers, and some Cherokees) fronts were 58.4",
rears were 57-59", depending on who you believe.
Wide tracks (some Cherokees) were about 6" wider
than that, or 62.5" in front according to Louie
Belt, who installed one. Kerry Embry claims narrow
fronts are 60.5" and wides are around 65". I
personally measured a narrow '82 Wag to be 61.5"
front and 58.5-59" rear. The pinion on an '87 GW
rear is offset 3/16" to the right. J-truck axles are
reportedly about 67" wide. Obviously, YMMV.
Brakes: Approx 12" front discs, 11x2" rear
drums.
Spline count: 30-spline D44's, 29-spline AMC
20's
Caster: 4-5 degrees
Other: All had Dana 44 fronts. '74-79 and
'86-91 had D44 rears, while '80-86 had AMC 20 rears
('86 could be either). '74-79 had passenger-side
front diffs; '80-91 had driver side diffs (needed
for YJ with stock t-case). Short side spring perch
partially overlaps the diff housing, but not bad.
The '87 front pinion is offset 8-7/8" left of
center. AMC 20 rears were 1-piece with 29-spline
shafts, but have narrower shafts & tubes than the
D44, and the tubes are therefore more prone to
bending at the housing, which causes breakage. Many
auto trannies had the Quadra-Trac t-case & severely
offset rear diff in '70's models. '86-91 rear D44s'
pinions are offset 3/16" right of center (with a 17"
driveshaft, that's a horizontal angle of 2.3
degrees). Part-time t-cases (Dana 20 or NP208) had
manual locking hubs, while full-time Quadra-Trac
t-cases (BW 1339, NP219, NP228, NP229) had fixed,
locked hubs. The NP228 & NP229 (mid '80's) also had
a vacuum disconnect front axle (like the YJ), which
is inherently weaker than the solid axle shaft (like
the TJ). |
Vehicle:
'78-79 Ford Bronco, F-150, F-250 (reverse-cut D44
front, left-hand drop) (F-150 had 9" rear, F-250 had
Dana 60)
Bolt pattern: 5 on 5.5" (Bronco and F-150) or
8-bolt (F-250)
Width: Way wide (~65")
Brakes: 11" discs
Spline count: 30-spline D44 front, 297 (large
style) U-joint
Caster: ???
Other: 297-style U-joints are stronger than
the EB flavor, and identical to the '95-present
Wrangler D30. The reverse-cut gears are inherently
stronger up front than standard-cut gears, and
provide a higher pinion with a better driveshaft
angle (just like the stock YJ D30). The Ford-style
manual hubs are internally-splined rather than held
on with 5 or 6 bolts like most others, which makes
them stronger and less prone to leakage. They can
also be combined with knuckles, spindles, and brakes
from a '74-76 SJ or Chevy D44 to get the high-mount
steering arms. F-250's had leaf-springs and 8-lug
wheels, while Broncos and F-150's had front coils
and 5x5.5" wheels. F-150/Bronco outers could be
swapped into an F-250 axle to achieve leaf springs
with a 5x5.5" bolt pattern, or you could just cut
off the coil suspension bracketry (no small task)
from an F-150/Bronco axle, or you could use an
8-bolt rear end to match the F-250 front. Another
big drawback is the width of the axle. Cutting it
down means a broken long-side axle shaft can only
fixed with custom hardware. Then again, it could be
cut to the same length as an SJ long-size shaft,
allowing use of an SJ shaft instead of a custom-cut
F-150 shaft. Front differential location (at least
on F-150/Bronco) is identical to the early Bronco
(3-4" closer to center than YJ D30). Like early
Broncos, the stock tie rod / knuckle mounting holes
lose turning radius, but this can be fixed with the
high-steering mod. Most (all?) F-250's came with
4.11 gears. Some 1/2-tons had 4.11's, though most
had higher gears. |
Chevy 1/2 and
3/4-ton pickups had standard-cut D44 fronts, but
they were full width and would have to be shortened
to work, eliminating any hope of finding stock
replacements if something broke. |
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