[Shorter than stock Wrangler T-case replacement]
Is also available, if you want to have the top of the line components and get the best of all. I use a 2.7 ratio Klune-V feeding a 4.3 ratio Atlas in my Grand Cherokee buildup. See combo comparisons at the bottom of this article.
Klune-V "Extreme Underdrive" Basic Information
Extreme Underdrive is an underdrive gearbox that
bolts in place between
the transmission and transfer case. we call it "extreme,"
because the underdrive multiplies your existing gear reduction by up to
4 times, rather than a usual underdrive of 1.2 times, or so. It is
intended for extreme four-wheel-drive applications, rather than towing
or gear splitting in a big truck. It works equally well with both manual
and automatic transmissions.
David crawler is intended primarily for short wheelbase applications where
extreme low-crawl gears are desired for moving very slowly and precisely
through difficult or very tight rock formations, and up or down
waterfall-type obstacles. The emphasis is on precision, skill and finesse.
While plenty stout, it is geared too low to be practical for hammer-down,
tire-spin applications. (If you need more tire speed, simply shift the
David into 1:1 ratio, leaving your transfer case in low range).
the other hand, the Goliath is intended for full-size, high-power hill
climbing, mud boggin' pulling and tire spinning. Strength and
unstoppability are the emphasis.
units are physically the same size, and have the same bolt pattern. These
units are new-manufactured, purpose-built units, which come with a full
one-year warranty. While similar to "dual transfer case" units
in function, they are not built up from cut or sectioned used transfer
You're a serious enthusiast, which means you've gone down the road and know what you want. You've probably beefed up your suspension, expanded to 33-inches or larger tires, and added a locker or two. You're having fun, you're moving over the environment in all its forms and challenges. There's just one more step to go to maximize your rig extremely low gearing for extreme high adventure. With the Extreme Underdrive you've gone high tech and really low gearing. How low can you go?
line, you'll be able to crawl up obstacles that previously were viewed as
insurmountable. Here's a real-world example from our R&D department
with Greg "Go-for-it" Miller behind the wheel. Here's the scene.
"We're tracking in twelve vehicles looking for action in Surprise Canyon. We run into a Close Encounter of the Watery Kind, seven waterfalls that by the old book would require winches to conquer. We took on three of them just for the fun of it. That's the point, isn't it? Loose rock, slippery rock, big rocks, moon rocks we'll take them all on. Course, we had an edge. First we let the non-Extreme Underdrive vehicles have a go at it. One, a Jeep did manage one of the seven waterfalls, although he did get sideways and take several passes to make it across. The other guys without Extreme Underdrive packages said let's break out the winches. Not us in the Toyota Mini Truck and the 1977 Bronco equipped with the Extreme Underdrive upgrade. Both rigs crawled up three waterfalls totally unassisted and without any thrashing. Talk about a trial by fire rather water!
you still get to keep your existing low range, and good highway gears.
Which Way Is Mount Everest?
You Can Crawl Over New Horizons What Else Does the Extreme Underdrive
about saving wear and tear?
about saving money?
Low Gearing Means Reduced Body Damage and Mechanical Breakage.
to stop or turn before that rock bites your quarter panel.
going slower, you control what you hit and how hard you hit it.
shock loads on axles, drive train and suspension.
Torque can be applied more smoothly, thereby less clutch stress.
physics that pay off in reduced repair, expenses and less down time.
are the alternatives?
you can go another route to get low gearing. But they're called
compromises for very good reasons.
axle gearing to real low gears.
You can get some lower gearing
You have to turn a zillion RPM at highway speeds. Not a good thing.
a two-speed T-case with deeper gearing.
It gets you somewhat lower and keeps highway driveability.
Loss of normal low range. And no super crawling.
Klune-V Extreme Underdrive's multiple low range provides the most
versatile gearing set-up available.
your vehicle is fitted with the "Goliath" Extreme Underdrive,
you receive three different Transfer Case ranges:
your vehicle is fitted with the "David" Extreme Underdrive, you
receive four different Transfer Case ranges:
What do the numbers mean?
Extreme Underdrive provides the most flexible set of options
available to respond to the wide range of environmental challenges you'll
It also means you can actually use your off-roader on the road to get to the off-road site.
For example: Say you have a stock Jeep with stock tires. It turns about 2700 RPM at 65 MPH. With 33s and 4.11 axles (or 35s and 4.56 axles), still close to stock and fairly civilized. You will maintain decent highway operation. But if you switch to 4.88 or deeper gears, the highway ride heads toward the unpleasant zone. Worse yet, these super deep-cut gears rely on a relatively small and thereby much weaker pinion gear.
Your Mud Wrestling Skills?
or mud driving usually requires high range or normal low range gearing. If
you are missing your normal low range, a result of switching to a lower
geared T-case, you'll find yourself stuck, literally,
unsatisfactory choice of either high range (not deep enough) or a too-deep
low range which restricts your tire RPM and as a result fails to pull you
lips sinks ships. Loose hill climbs pose other problems.
low range (about 20-30 to one ratio) tends to work best for scaling loose
hills. Scrambling helps maintain the momentum to keep forward-ascending
motion. On the other hand, hard, technical rock crawling will be best
enjoyed, and accomplished, using much deeper gears. If you venture onto
"Sledgehammer" type trails, youčd probably opt for a setting
130-225:1. Less than that and you'd be reaching speeds too fast for
our trip to Surprise Canyon and those slippery waterfalls?
"It's no surprise that we found a ratio of 145-225:1 best suited to keep you smoothly moving over the rocks and crawling up the falls. That's on the way up. Gravity wanted to drag us down; the Extreme Underdrive took us over the top. On the return trip, we got the best control from the 60-130:1 range. Now gravity tries to throw you down the mountain. Go too low, and you won't be able to scoot if you need to correct a potential end-do situation. Extreme Underdrive Super Crawling made it a walk on the wild side but with total control.
we had the water world experience in the canyon environment, and we looked
for another dimension. Someone said Moab. They've got slick rock that gila
monsters can't even hold onto. We blasted up Interstate 15 to Utah, then
left it for some ledge climbing. Walking the ledge keeps you on your toes
and the edges of your treads. The slick ledge rock responded best to 60:1
for climbing; slow enough for control, but enough momentum to get up the
ledges you can't straight crawl up. Going down, we opted for 145:1 as you
kind of "lowered" yourself down ledges, still keeping control.
transitions between more challenged sections, like on easier trails, we
selected standard low range or 4.0:1 for best results. Extreme crawl is
too low. Too many RPM, too much buzzing.
"Final summary: For serious Technical Rock, go for at least a 130:1 final drive."
So you want to go off the beaten path? Can you dance?
You're an experienced off-roader. You can walk the walk, dance the dance, but now it's time to learn to crawl Extreme Crawl. The traditional off-road driving method called "Off-road Dancing" involves coordinated tap-dancing on the brakes, clutch and gas pedal to wrangle your way through the tough spots. Good tricks of the sport and valuable survival skills, but it's time to enroll in Extreme Underdrive School for the latest n super crawl driving techniques.
Basic Dance Steps to Best Enjoy Extreme Crawl
OFF THE THROTTLE!
Some trail or rock conditions require a measure of tire spin to negotiate, especially mud. Use Normal Low Range or High Range. This is not a crawl application.
IS NO LONGER