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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.