SLIP YOKE ELIMINATORS - 101
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
Changing your ring and pinion ratio and/or tire size will cause an inaccurate
reading of your speedometer. Replacement of the speedometer gear is a simple
procedure that takes minutes to complete. The chart below lists ring and pinion
ratios and tire size. Simply select the proper configuration of your vehicle from the
An accurate speedometer reading is important both on and off road when detailing
travel routes and for on highway safety.
Factory speedometer variances are ±3% from actual speed. Recommended
speedometer driven gears are based on a manufacturers published tire specs for
revolutions per mile. This may differ from manufacturer to manufacturer.
Standard Short ShaftSpeedometer Gear Chart
Fits 231-J transfer cases only
Earlier 231 applications with mechanical speedometer cable require updating to an electronic speedometer.
Yoke and Nut
- Transfer Case Model: NP231
Jeep Wrangler (TJ)
- 2006 Jeep Wrangler (TJ)
- 2005 Jeep Wrangler (TJ)
- 2004 Jeep Wrangler (TJ)
- 2003 Jeep Wrangler (TJ)
- 2002 Jeep Wrangler (TJ)
- 2001 Jeep Wrangler (TJ)
- 2000 Jeep Wrangler (TJ)
- 1999 Jeep Wrangler (TJ)
- 1998 Jeep Wrangler (TJ)
- 1997 Jeep Wrangler (TJ)
Jeep Wrangler Unlimited (TJ)
- 2006 Jeep Wrangler Unlimited (TJ)
- 2005 Jeep Wrangler Unlimited (TJ)
- 2004 Jeep Wrangler Unlimited (TJ)
Jeep Wrangler (YJ)
- 1995 Jeep Wrangler (YJ)
- 1994 Jeep Wrangler (YJ)
- 1993 Jeep Wrangler (YJ)
- 1992 Jeep Wrangler (YJ)
- 1991 Jeep Wrangler (YJ)
- 1990 Jeep Wrangler (YJ)
- 1989 Jeep Wrangler (YJ)
- 1988 Jeep Wrangler (YJ)
- 1987 Jeep Wrangler (YJ)