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Dual Transfer Cases: Land Cruiser + NP203

Introducton:

With limited options for extra low range gears the new Advance Adapters (AA) NP203 conversion kit is long over due. This new kit mates the gear reduction section of the NP203 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 drivetrain length. Moving the engine forward may be a must for most applications. I removed my mechanical fan and used a pusher fan that required extra modification to the front of the Cruiser. This change resulted in a 4" savings that was used to keep the rear driveline from being to short. The NP203 case will lengthen your drive train 6.5" with the SM465 transmission as compared to the stock AA SM465 adapter.

NP203 To Transfer Case Preparation:

The first part of the project is to obtain an NP203 transfer case. Be sure you get a transfer case with the adapter for your transmission. You do not need the shifter mechanism but you will have 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. You will not need to remove the rear adapter or shaft to separate the two halves. 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 in the rear half 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 thrust washer, gear, bearing, and cover from the shaft. Keep these parts. Cut off half of the bump on the cover plate. Check for clearance with the AA adapter.

Install the NP203 bearing and cover on the new shaft. Place the shaft bearing back in the cover and retain with clip. Place the unit on the new shaft. 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. Grease the new shaft end hole to retain the needle bearings during assembly. Be sure you have 15. 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.

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 hole and use a hose nipple for future filling. You may need to cut a 1" access hole 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 foraged.

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.

Assembled, the components are (left to right): 1) AA rear transfer case mount, 2) Toyota 1977 FJ-40 "4 speed" transfer case, 3) AA adapter (silver), 4) NP203 transfer case gear box section (redish), 5) NP203 factory SM465 adapter (bright black). Note the round object at the center of NP203... it is the shifter bolt for the NP203.

Shifter Mounting Bracket:

Attach the new shifter mount 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 Dual Cases To The Transmission:

Attach the NP203 to the transmission. In my case, 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. 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 and mount could be used.

Shifter Installation :

The Cruiser transfer case shifter assembly will be attached to the NP203 with a fabricated bracket (drawing). 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.