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Teraflex 4444400 231 Extreme Short Shaft Kit for NV231-J Transfer Cases

Catalog #: 52237.900
Teraflex Part #: 4444400
The Extreme Short Shaft kit is what short wheelbase Wrangler owners have been dreaming of for decades. The Extreme kit not only improves on strength, but also increases driveshaft lengths by up to 7" over a stock application. It is over 3" shorter than a standard SYE kit, and 1-1/2" shorter than an ATLAS II. The Extreme SS kit comes with all necessary components to modify the stock 231 case. Speedometer readings are transferred through a tone ring and electronic sensor. To adjust the calibration a converter box is necessary to make any calibration adjustments.

Most 231 transfer cases came from the factory with a slip-yoke rear output (see bottom photo). This slip yoke will slide or slip in and out of the rear of the transfer case as the suspension cycles up & down. When driveshaft angles are changed due to suspension height or suspension travel the slip yoke is forced to operate at an angle and can cause binding, and in some situations will crack the case.
Another problem with the slip yoke design is that the rear driveshaft yoke cannot be removed from the vehicle without loss of transfer case fluid.
Broken u-joints can often require the vehicle to be driven back off the trail with the front driveshaft only. Without eliminating the slip yoke on the
rear output, this would be impossible without losing the transfer case fluid, and causing transfer case damage.
On any short wheel base vehicle (such as the Wrangler), driveshaft angle is very critical and
must be addressed when making any suspension modifications. Standard factory Wrangler
driveshafts are about 12". This short driveshaft will cause severe vibration and premature u-joint failure if not upgraded.
A Short Shaft kit, or Slip Yoke Eliminator solves the short driveshaft length, allows driveshaft removal in the event of a u-joint failure without loss of fluid, and increases the output shaft strength dramatically allowing for increased
power and torque to be transferred to the wheels for traction.
There are several approaches to Slip Yoke Eliminator kits. Some use a "hack & tap" method which results in a lower priced kit, but does not effectively increase any strength, and can actually increase driveshaft vibration. TeraFlex was one of the innovators that developed a completely new heavy duty output shaft that can increase
torque loads by nearly 50%, as well as offer solutions to the original slip yoke problems. TeraFlex has perfected low range gearing and continues to lead the industry in quality performance transfer case products.
Top Photo: Extreme Short Shaft SYE
Middle Photo: Standard Short Shaft SYE
Bottom Photo: Stock Slip-Yoke

The Extreme Short Shaft kit does not use the traditional "speedometer gear" to
calibrate the speed of the vehicle. We have updated the signal to a digital reading
(similar to 03+ Rubicon). This allows a more accurate reading. The chart below
gives you the configuration of your vehicle by comparing tire size and axle ratio.
If your selection of tire size and gear ratio do not yield a result that is within the
green acceptable range a converter box will be necessary to make any calibration
An accurate speedometer reading is important both on and off road when detailing
travel routes and for on highway safety.
Factory speedometer variances are Ã?�Ã?±3% from actual speed. Recommended
speedometer driven gears are based on a manufacturer's published tire specs for
revolutions per mile. This may differ from manufacturer to manufacturer.
Extreme Short ShaftSpeedometer Calibration Chart

Installation Notes
Installation Difficulty:
Level 3Advanced

Fits 231-J transfer cases only
Earlier 231 applications with mechanical speedometer cable require updating to an electronic speedometer.

Installation Time: 2-4 hours
Parts Included

Output Shaft
Output Housing
Speed Sensor Ring
Yoke & Nut
Installation Hardware

  • Transfer Case Model: NP231
  • Jeep Wrangler (TJ)

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