28 OCTOBER 2019 4-WHEEL & OFF-ROAD 4WHEELOFFROAD.COM
JUNKYARD AXLE SPOTTER’S GUIDE
STERLING 10^1 ⁄ 4 & 10^1 ⁄ 2
Identification: 12-bolt cover, 12^1 ⁄ 2 inch-
es wide, full-floating design (some 10.25
axles were semifloating).
Specs: 101 ⁄ 4 -inch ring gear (1985-1998),
101 ⁄ 2 -inch ring gear (1999-newer), 35-spline
axles, 3.08-5.38 gear ratios, eight-lug.
Found In: Rear of 1985 and bewer F-250
and F-350 trucks; most common in 1999 and
newer Super Duty trucks and Excursions.
The Good: These axles were developed
by Ford to replace the Dana 60 and Dana
70 axles and have a good reputation for
strength and durability. Though some 10^1 ⁄ 4 -
inch axles were semifloating, all 10^1 ⁄ 2 -inch
Sterling axles have a full-floating design.
The Bad: The earlier 10^1 ⁄ 4 axles have a
few weaknesses that were addressed with
the later 10^1 ⁄ 2 design. There are also some
oddball 10^1 ⁄ 4 -inch semifloating applica-
tions, such as the short-lived, light-duty,
seven-lug F-250, which should be avoided.
Locker selection and axle ratios are not as
good as other applications, and there are
some year splits for gears and overhaul
kits that anyone should research before
ordering replacement parts. Though it’s
rare, we have seen Sterling housings spin
the axletubes under extreme use.
Notes: These axles have been the
primary rearend for Ford’s Super Duty
trucks since the term was coined in 1999.
Equivalent to a Dana 70 and stronger on
paper than a Dana 60, these axles are a
good choice and a popular one for JKs on
40-inch and larger tires. Like all Super Duty
axles, most Sterling 10^1 ⁄ 2 -inch full-floating
axles use an 8-on-170mm bolt pattern.STERLING 10^1 ⁄ 4 & 10^1 ⁄ 2GENERAL MOTORS
GM 71 ⁄ 2 -INCH
Identification: Squarish 10-bolt differ-
ential cover, 8^3 ⁄ 4 inches wide, smooth bot-
tom (no protruding bosses like a 10-bolt).
Specs: 71 ⁄ 2 -inch or 7^5 ⁄ 8 -inch ring gear,
26- or 28-spline semifloating axles, 2.73-
4.56 gears, five-lug.
Found In: Rear of S -10 Blazer s , A stro vans ,
and pickups; various car applications.The Good: Not much to say here other
than they seem to live if you leave them
alone. We’ve included this light- duty axle
mostly to identif y what to stay away from.
The Bad: These axles are marginal for
stock applications and will not hold up to
large tires and abuse. Differential selec-
tion is limited , as is gear ratio selection.
Notes: Unless you’re considering an
axle swap into a lightweight vehicle like a
Samurai, these are not the axles for your
build. Even then, far better choices can be
had for about the same money with many
more differential and gearing choices.GM 7^1 ⁄ 2 -INCHGM 10-BOLT
Identification: Mostly round 10-bolt
cover with a slight bulge on the left-hand
side, 11-inch-wide cover, two bosses at 5
and 7 o’clock.
Specs: 8.5 -inch ring gear (1979 -1998),
8.6-inch ring gear (1999-current), 28- or
30-spline axleshafts (depending on year)
semifloating C-clip axles, 2.73-5.57 gear
ratios, five- or six-lug.
Found In: Front of 1973-1987 GM trucks
and 1977-1990 Blazers, Jimmys, and Sub-
urbans; rear of 1979-2013^1 ⁄ 2 -ton trucks
(depending on the application); select S-10,
Trailblazer, and Colorado applications.
The Good: These axles are reasonably
strong and durable in stock applications,
but other than that, there’s not much
good to say about them.
The Bad: They become marginal whenadding bigger tires and traction-adding
devices. The front (solid axle) applications
are roughly equivalent to a Dana 44 but do
not enjoy the same aftermarket support.
The rear axles are all a C-clip design, and
the shafts themselves are prone to failure
when subjected to abuse. Though com-
mon, these axles are far from ideal.
Notes: These axles should not be confused
with 10-bolt car axles, which have little in
common with the truck 10-bolts. History and
practical experience have shown that these
axles survive fairly well in stock applications,
but their shortcomings start showing up as
soon as they are modified or subjected to a
heavy right foot. With heavier 14-bolt axles
being so prevalent and cheap, it’s hard to jus-
tify putting any money in one of these axles.GM 10-BOLTGM 12-BOLT
Identification: Irregular 12-bolt differ-
ential cover, 11-inch-wide cover.
Specs: 87 ⁄ 8 -inch ring gear, 30-spline
semifloating C-clip axles, 2.76-5.13 gears,
five- or six-lug.
Found In: Rear of various 1963-1981(^1) ⁄ 2 -ton truck applications.
The Good: These axles have a pretty
respectable reputation and can easily
stand up to 35s and locking differentials
with conservative driving. We’ve beat on
a few 12-bolts and have been impressed
with what they can withstand.
The Bad: C- clip axle design leaves much
to be desired , and it’s hard to justif y put-
GM 12-BOLT