Pirate4x4.Com - Pirates of the Rubicon 4wd Club

Notice: These instructions are provided as a guide only. No responsibility is assumed for errors, damage, or injury that may be caused by their use. Always use the proper safety equipment when working on projects such as this one.

With limited options for extra low range gears the new Advance Adapters (AA) NP 203 conversion kit is long over due. This new kit mates the gear reduction section of the NP 203 transfer case to the front of a "four speed" Land Cruiser transfer case giving a four to one low range. Adding a transfer case uses up space. Moving the motor forward may be a must for most application. I changed my mechanical fan to a 1" slim fan and used an electric pusher fan on the front of the Cruiser. This change resulted in a 3" savings that can be used to keep you rear driveline from being to short. The NP203 kit will lengthen your drive train 7" with the SM465 transmission.

NP203 to T-case Preparation

The first part of the project is to obtain an NP203 transfer case. Be sure you get a case with the adapter for your transmission. You do not need the shifter mechanism but you will need to make two less parts if you do get one. This unit is VERY heavy and you won't be able to move it yourself. Next disassemble the two halves of the transfer case by removing the output shaft nut and bearings.

It is recommended that you have a manual for the NP203 on hand to refer to. Don't worry about the roller bearings when they fall out as you won't need them. Once you have the two halves apart you can discard the little shifter connecting rod between the two cases. Carefully remove the main shaft and fish out the 15 needle bearings for future use. Remove the trust washer, gear, and bearing from the shaft. Keep the big bearing , ring clip, gear, and cover plate. Cut off half of the bump on the cover plate as shown in the photo. Check for clearance with the AA adapter.

Install the NP203 gear on the new shaft.

Place the shaft bearing back in the cover and retain with clip. Place the unit on the new shaft. Grease the new shaft end to retain the needle bearings. Be sure you have 15. File any burs on the old NP203 gear that meshes with the gear on the new shaft. Test to see that it will mate with the gear on the new shaft before you put it together.

Next slide the shaft assembly into the NP203. Note placement of the gear set. Once assembled do not try to test shift the NP203 gear as the unit will fall apart. Even installed in the truck the unit by design will be hard to shift so you will not be able to test shift it out of the truck. Install the bolts.

Shifter Mounting Bracket

Attach the new shifter mounting bracket to the NP203 with the transmission adapter bolts. It was fabricated from angle iron with flat bar welded to it for the NP203 shifter.

Attaching The Adapter to the NP203

Attach the AA adapter to the NP203. Lock tight is recommend for all bolts. Install the drain plug NOW. You will need to use the vent at the top of the unit to fill the case with oil so don't put in the vent cap yet. It is recommended that you thread the vent cap whole and use a hose nipple for future filling. See photo 4. You may need to cut a 1" access whole in the transmission hump to access and fill the unit in the vehicle. Attach a long hose to allow for placement of the end above any water that may be forged.

Combining The Two Transfer Cases

Combine the NP203 with the Land Cruiser transfer case. . Double check that the NP203 drain plug in the adapter is installed. When putting the shaft through the case be sure to place the gears correctly. Attach the new shaft nut.

Attaching Dual Cases To The Transmission

Attach the NP203 to the transmission. In my cases the transmission was in the Cruiser. You have two choices for supporting this assembly. First is the AA support that attaches to the rear of the transfer case. See photo 5. The second is a custom support for the NP203. The latter has a support mount built in. Check for driveline angles etc. In this case the engine was moved forward the exact amount that this new application extended the drive train so the original drive lines could be used.

Shifter Installation

The Cruiser transfer case shifter assembly will be attached to the NP203 with the bracket. Note that this bracket will also be used for the shifting the NP203. Attach the Toyota shifter first. The bracket on the NP203 that shifts the shaft may need to be shortened so that it clears the cases. Attach the old shifter linkage rod to the NP203 and the shifter.

It will need to be reshaped to fit properly. The design with the linkage was chosen to move the NP203 shifter forward of the Toyota case shifter and to reduce its length of throw. This will keep them from hitting each other and allow for a boot to cover them. You may find that another method will work better for your application. The dual shifter boot was purchased at Capitol Jeeper's Supply in Sacramento California. Ask Gary for the offset dual shifter boot that has square bases and he will know which one you need.

NP203 Shifter Handle

The NP203 shifter was made from flat bar and rod. You may choose sizes that are best for your application but keep in mind that a moderate amount of force will be used to shift.

Operation

I have found that it is much easier to shift the NP203 into low range than to high. It makes a bit of a disturbing noise as the gears mesh. I leave the NP203 in low while on the trail. Be careful of the higher amount of torque that is produced in double low range.