Installing the Tera 2Low231 Kit

The 2Low231 Kit from Teraflex comes with a new sector and mode fork

Have you ever been in a situation where you're engaged in 4wLo, traversing some nice slick rock and then have to make a really tight turn?  If you have, you know how difficult it can be to make that turn while engaged in 4wLo.  The front seems to want to really grab the rock, making it hard on you and hard on your equipment. This situation is common to rigs that don't have a means to disconnect the front driveshaft only, yet still need to have the low range 4 wheel drive. Depending on your make and model, there are several options available. For the Dana 300, you can install a twin stick that will allow you to disengage the front driveshaft, yet remain in 2wLo.  But for those of us that run the stock NP231 transfer case, the twin stick isn't an option. Another product on the market replaces the stock vacuum disconnect with a cable to manually disengage the front passenger side axleshaft, yet the front driveshaft remains engaged.

The solution?  Install a 2 wheel low kit in your NP231 transfer case.  The kit, offered by Teraflex, is called the 2Low231 kit.   Once installed, it will free up the front axle for better steering while keeping your low range. Now you can choose between either 4 Low or 2 Low. The 2 Low will eliminate drive train bind and most of your three-point turns. The 2Low231 kit provides a mechanical disconnect for the front and rear output shafts while in the neutral shift position, thus allowing for a "true neutral". When engaged in 2 Low, the front axle vacuum disconnect is deactivated allowing for independent rotation of the right and left front axles. The "4WD" dash light is also deactivated while in 2WD low range.

The stock sector on the left compared to the new 2Low231 on the right.

The kit is manufactured for 1988-present Jeep Wranglers and Cherokees with the NP231J transfer case and comes with instructions, a new sector and mode fork CNC machined from 4140 steel, and heat treated for added strength. Since this installation only involves changing some internal parts, there are no external modifications required for the shift linkage or body. This kit is also fully compatible with the "Slip-Yoke Eliminator Kit" and 4-to-1 planetary gear set.

INSTALLATION:

The instructions that were included in the kit start at the point where the transfer case has already been removed from the vehicle and the case separated.  Since this was my first time removing a transfer case, I thought it would be helpful to review the steps required to remove the transfer and separate the case halves and install the new parts. These steps should only be used as a referrence. Always follow the instuctions included in the kit and when possible, follow the directions in the service manual.  As a side note, the Haynes manual I have for my Jeep does not provide any detail on the removal or service of the NP231 transfer case.  A Factory Service Manual would be the reference of choice.

1. Drain the transfer case fluid and then support the transmission and the transfer case with jack stands,

2. Remove the transfer case skid plate, front driveshaft and rear driveshaft,

3. Disconnect the speedometer cable, electical lines and vacuum lines from the transfer case,

4. Remove the six nuts that attach the NP231 transfer case to the transmission. Once the nuts are off, slide the transfer case off the transmission and remove it from the vehicle,

5. Once the transfer case has been removed from the vehicle, set it on a workbench or other solid surface. Remove the front driveshaft output yoke. Remove the oil pump housing nuts and remove the housing.  Remove the c-clip that retains the output shaft (on the transmission side),

6. Remove the speedometer gear unit and remove all the bolts that hold the tail cone to the tail housing, and remove the tail cone. Remove the c-clip that retains the rear output shaft,

7. Remove all the bolts that hold the tail housing to the front case half and remove the tail housing,

8. Removed all the bolts that hold the transfer case together and pry the case apart,

9. Once the case has been separated, remove the top half of the case,

10. Gently pull the output shafts up and remove both along with the drive chain,

The NP231 Transfer case removed	View showing the transfer case separated

Remove the sector and mode fork and install the new ones. Be sure to install the mode fork spacers.

View of the new sector and mode fork	Looking at the new sector and mode fork installed

After the new parts are installed, re-install the gears, output shafts, drive chain and front output yoke. Apply a good silicon sealer to the case and attach the case halves together. Re-install the c-clip from the front output shaft, re-install the oil pump, tail cone assembly, speedometer gear housing and torque the bolts to spec.  Install the transfer case back into the vehicle, attach the driveshafts, skid plate and fill the transfer case with fresh ATF fluid. Test to make sure it shifts into gear and there is no interference with the body tub.  You may need to adjust the shift linkage to get it to shift into all gear ranges.

Teraflex Dept ORN Phone 801.256.9897 Fax 801.256.9879 e-mail: teraflex@vii.com

• Comments or Questions
• JeepTech Page
• JeepWire Page