34 OCTOBER 2019 4-WHEEL & OFF-ROAD 4WHEELOFFROAD.COMJUNKYARD T-CASE SPOTTER’S GUIDE
DOMESTIC (Alu minu m)
NP/NVG 231
Overview: Depending on when it was
manufactured, the label will say “NP”
(New Process) or “NV ” (New Venture Gear).
Either way, the NP231 might be the most
common transfer case you’re likely to
find in a modern 4x4, with a variety of
input spline counts and at least a couple
mounting patterns and clocking. Prede-
cessor is the NP207, which is similar but
less desirable. The NP231 and other NP
T-cases have a three-number designa-
tion that indicates (A) number of speeds;
(B) strength; and (C) type, as in part- or
full-time and shift type (manual, electric),differential and type, gerotor, or viscous
coupling. For example, an NP233C is an
electric-shift, two-speed, part-time trans-
fer case found in Chevy 4x4s.We are going
to focus on manual shift cases most likely
to be used or swapped in.
Found In: 1988-present Jeeps, including
Wrangler, Cherokee, Comanche, Liberty,
and Grand Cherokee. Also in GM S- series
4x4s, Dodge Dakotas, and 1500 4x4s.
Identification: Aluminum three/four-
piece housing, manual shift, rear slip-yoke
housing. Best identified by the round tag
on the rear of the case.
Low Range Ratio: 2.72:1
Modifications: Aftermarket 4:1 gears
and half-case were available from Teraflex
and can be had on the used market. 2-low
conversion for some NP231s. Various
shifters; wide chain; six-gear planetary;
heavy-duty slip-yoke eliminator.NP/NVG 231NP/NVG241
Overview: Slightly larger than an
NP231, the NP241 is rated for more torque
input (around 1,900 lb-ft for the NP231 to
5,555 lb-ft for the NP241). A very common
transfer case in^1 ⁄ 2 -ton 4x4s from the late
1980s into the late 2000s.
Found In: 1987-2002^1 ⁄ 2 - and^3 ⁄ 4 -tonDodge pickups; 1987-1993 Ramchargers;
1989-2012 Chevy pickups.
Identification: Aluminum three- or four-
piece housing, manual shift, rear slip-yoke
housing. Best identified by the round tag
on the rear of the case. Slip yoke front
housing on some cases.
Low-Range Ratio: 2.72:1
Modifications: Slip-yoke eliminators.
Shifters are available for the NP241.NP/NVG 241NV241OR
Overview: As with all transfer cases,
there are lots of variations in the NP/
NV241, but the NV241OR is really an
entirely different transfer case. Designed
to add lower gearing to the factory rock-
crawler, the Jeep Wrangler Rubicon.
Found In: 2003-2019 Jeep Rubicon
models only.
Identification: Aluminum case with
standard Jeep/GM/Dodge six-bolt front
pattern. The housing then widens quickly
with a large 12-bolt bearing retainer/
planetary cover. Look at the tag. Avail-
able with both 23- and 26-spline inputs.
Fixed outputs.
Low Range Ratio: 4:1
Modifications: Cable shifters.NV241ORNP242
Overview: The NP242 is basically an NP/
NV241 but with a lockable center differ-
ential. That means the vehicles equipped
with this T- case could be driven on - road
while in “ full-time” 4WD. That’s nice if you
live where it snows, or drive on gravel
roads a lot. This is a fairly durable unit in
smaller to midsize 4x4s.
Found In: 1987-2012ish Jeeps, includ -
ing Wrangler, Cherokee, Comanche, Lib-
erty, and Grand Cherokee; 1984-present
AMG HMMWV (Humvee); 1992-2006 GM H1.
Identification: Aluminum three- or four-2893 AMERICAN WAY, OGDEN, UT 84401
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