4WHEELOFFROAD.COM 4-WHEEL & OFF-ROADNOVEMBER 2019 65
ROCKWELL 2.5-TON FRONT/REAR
FOUND IN: Military M35A2 2.5-ton 6x6 trucks
WIDTH BETWEEN WHEEL MOUNT SURFACES: 79½ inches (hubs out)
or 69¼ inches (hubs flipped)
SHAFT DIAMETER/SPLINE: 1.62-inch, 16-spline
COMMON GEARING: 6.72
BOLT PATTERN: 6-on-8¾
PROS: They’re strong and inexpensive to buy when compared with 1-ton
Dana axles. The double-reduction style centersection can be flipped with
a little wo rk to h elp in d rivet rain clea ra n c e. Af terma rket steerin g a rms
and pinion brake components can be bought or fabricated relatively
cheap. They’ll stand up to a good deal of abuse with tires up to 45-inches.
CONS: Th e shaf t s a ren’t m etallurically as st ro n g as m o d ern of ferin gs , so
46-inch and larger tires can take their toll. Additionally, the 6.72 gearing
and huge physical size favors at least a 42-inch tire and creative fitment
to clear engine and drivetrain. In addition to the small tire size window,
the bolt pattern will really limit wheel selection. Once you get into
aftermarket shafts and at-the-wheel disc brakes things get expensive.
Rockwells are best run in stock (or near-stock) form or not at all, but if
you’re running high-horsepower and big meats you’ll have to have really
deep pockets to keep your Rockwells alive.FSJ DANA 44
FOUND IN: ’74-’91 Wagoneer, Cherokee, Cherokee Chief, J-truck
WIDTH BETWEEN WHEEL MOUNT SURFACES: 59½ inches (narrow-track
Wagoneer/Cherokee S front); 58½ inches (narrow-track Wagoneer/
Cherokee S rear); 66 inches (wide-track Cherokee Chief/J-truck front);
65 inches (wide-track Cherokee Chief/J-truck rear)
SHAFT DIAMETER/SPLINE: 1.31-inch, 30-spline
COMMON GEARING: 3.23, 3.54, 4.09
BOLT PATTERN: 6-on-5½ or 8-on-6½ (some ¾-ton J-trucks)
PROS: T h e Q ua d ra -Track FSJs have Da na 4 4 rea r a xles of f set to t h e
passenger-side, which makes use in early Spicer 18-equipped Jeeps
nice. The width is more manageable in most CJ and Universal vehicles,
and when used with a spring-under front suspension the stock steering
can be adapted with little trouble.
CONS: The 6x5½ bolt pattern is only easily converted to 5x5½ on the ’74-’76
small-bearing spindle models. Some early ’80s fronts were a CAD vacuum-
disc o n n ec t d esign t hat sh o uld b e avoid ed. N o rmally have to o ut b oa r d t h e
spring perches on CJ and YJ Jeeps unless narrowing long-side tube.GM 14-BOLT REAR
FOUND IN:’73-’01 GM ¾- to 1-ton pickups, vans, Suburbans
WIDTH BETWEEN WHEEL MOUNT SURFACES: 67½ inches (pickup/
Sub urb a n); 70 in ch es (va n); 72 in ch es (d uallie pickup)
SHAFT DIAMETER/SPLINE: 1.5-inch, 30-spline
COMMON GEARING: 4.11, 4.56
BOLT PATTERN: 8-on-6½
PROS: You can find this 10.50-inch ring gear axle at virtually any junkyard
and take it with you for $75-$200 depending on your location. Parts are
easily obtained and it uses one of the least-expensive Detroit Lockers
offered thanks to its sturdy factory split-case carrier. They’ll stand up to
huge abuse and 44-inch tires in stock form.
CONS: The bottom of the differential hangs pretty low, so large tires or
cutting the pumpkin are necessary for good ground clearance. The
1-to n d r um b ra kes a re massive, so s wa p pin g to af terma rket disc b ra ke
b racket s w it h jun k ya r d ½-to n calip er s may b e d esired.FULL-SIZE DANA 44 (GM/DODGE)
FOUND IN: ’73-’77 Chevy ½- and ¾-ton pickup, Blazer, Suburban;
’80-’84 Dodge ½- and ¾-ton pickup and Ramcharger
WIDTH BETWEEN WHEEL MOUNT SURFACES: 69 in ch es (Ch ev y);
67 inches (Dodge)
SHAFT DIAMETER/SPLINE: 1.31-inch, 30-spline
COMMON GEARING: 3.23, 3.54, 3.73, 4.09, 4.56
BOLT PATTERN: 5-on-5½ (Dodge ½-ton); 6-on-5½ (Chevy ½-ton); 8-on-
6½ (Chevy/Dodge ¾-ton)
PROS: They’re still easy to find in junkyards and have one of the strongest
aftermarket support systems in place. All Dodge and some Chevy versions
have flat-top knuckles for conversion to crossover steering in spring-over
applications. Dodge ¾-ton housings have shorter distance between ball
joint s , so s wa p pin g to ½ -to n k n u ckles allow s lon g -sid e to b e sh o r ten ed
for narrower WMS measurement and still work in many 4x4s without
outboarding springs. Chevy versions can be swapped to 5-on-5½ Ford
hubs/rotors easily. Almost all ¾-ton versions came with 4.09 or 4.56 gears.
CONS: M ost d o n’t wa nt to sh or ten lo n g - sid e tub e a n d/or o ut b oa r d sp rin gs
for use in CJs and YJs. Dodge knuckle versions are unique with few
interchangeable parts between other brands or even between ½- or
¾-ton Dodge axles. To go from ½- to ¾-ton you must swap whole knuckle.