66 Jp jpmagazine.com NOVEMBER 2019
By Trenton McGee
[email protected]YOUR JEEP
JL Lifts and Gearing
I am the proud new owner of a Jeep JL
Rubic on. My f ir s t ques tion is on gearing. In
one of her columns, Nena once mentioned
lowering the gearing to 4:56 from the stock
4:10. My research is indic ating that the
8 speed sometimes hits 7th and barely hits
8th with stock gearing, so does the 4:56
solve this? Mine is a daily driver and I wish
to retain all the roadworthiness I can. I’m
kind of leaning toward 4:88. My second
question is about lifts. I understand that
2.5 inches is the minimum I need to fit 37s
on a Rubicon JL. The dealership even says
they install the Mopar 2-inch and run 37s
all the time (with shifting issues mentioned
earlier about 7th and 8th, but no codes).
Many of the 2.5 - inch k it s re t ain the s toc k
control arms and have a lowering bracket
as one recently installed in your publica-
tion. Others come with new lower control
arms and sometimes new uppers too. I’m
leaning toward LCA kits due to the idea
of having the lowering bracket (midship
ground clearance) hanging below the
frame defeats the purpose of lifting it. As
I’ve asked before, what would you do?
Steven R.
Via email
You didn’t mention which engine you
have in your JL, and it’s an important
consideration when you start talking about
gearing. We suspect you have the 3.6L,
which is an adequate (if not especially
powerful) engine. The new 2.0L engine is
a rocket ship, and we’re anxious to start
playing around with one and see how
the smaller-displacement engine with
electric-assist handles a taller and heavier
tire and wheel package. It remains to be
seen how the 2.0L will do, but the 3.6L is a
well-known entity.
In some ways, the modern six- and
eight-speed transmissions let us “get
away” with larger tires without changing
the axle gears because the greater number
of transmis sion gears help to keep the
engine within its optimum powerband.
As you suspected, however, larger tires
with the factory gearing does render the
higher gears useless, so you can expect
performance and gas mileage to suffer.
The only way to restore the usefulness of
those gears and also regain some of the
fuel mileage lost is to re-gear the axles. We
would hesitate to go through the expense
of a gear c hange just to go from 4 .10 s to
4.56s if 37s are in your future. The math
actually makes a strong case of going to
4.88s with 37s, and we’d even consider
going to 5.13s if we wanted a little extra
pep off the line. Again, the excellent
gearing choices of an eight-speed make it
more forgiving to err a little on the low side
without any real drawbacks.
As for the lift kits, we’d recommend
doing a 2.5-inch lift with 37s if you want
to avoid any trimming and you intend to
actually use the Jeep off the pavement.
You’ll appreciate the extra ground clear-
ance, and the tires will have a little extra
room to move in the wheelwells without
touc hing sheetmetal or plastic. The JLs
have longer control arms than the JK, so
there’s less impact on the operating angle
of JL c ontrol arms than JK c ontrol arms
when you add lift height. That said, JLs are
extremely sensitive to changes in caster,
and caster is one of the things that changes
when you add ride height. Lift manufac-
turers c orrec t c aster by either providinglonger lower control arms or adding a drop
bracket to the lower arm. Like you, we’re
not big fans of drop brackets because they
reduce ground clearance and actually
place more stress on the factory frame
mounts. If we were in your shoe s, we’d opt
for a lift that includes lower control arms
rather than drop brackets. Upper control
arms are largely unnecessary with just 2.5
inc he s of lif t, so we’d skip them unle s s you
just like spending extra money.Drippy Wrangler
I have a 1994 Jeep YJ with a straight-
six and an automatic transmission. The
automatic has its own cooler and fan
on the wheelwell, and I am running an
electric fan on the radiator. I did not have
any overheating problems with the stock
radiator, but the old radiator has sprung
several leaks and I am looking to buy a
new or rebuilt one. Any recommendations
for the best radiator for the money for my
application would be greatly appreciated.
Are the aluminum ones really worth the
extra money?
Damon H.
Via emailWe’ve never been huge fans of the
plastic tank/aluminum-core radiators that
seem to be in all newer vehic le s the se
days, and this is likely the same type of
radiator that’s under the hood of your
Wrangler. They often spring leaks where
the tanks meet the aluminum core, and
what’s worse, you can’t just solder one
back together should you punch a hole
in it like you can a more traditional brass
radiator. The trouble is, you really aren’t
going to be able to upgrade over what you
have using stock replacement parts. A
quality aluminum radiator will last quite a
bit longer than a stock replacement, but as
you point out, they are more expensive.
If your Jeep’s radiator is leaking around
the tanks or even has a cracked tank,
there’s a chance you can have it repaired
at a local radiator shop, which would be
cheaper than buying a new stock replace-
ment. You mentioned that the Jeep wasn’t
overheating before, so that indicates the
c ore is probably in good shape, and a