P.O. Box 247, 4320 Aerotech Center WayNew Item: (12/98)
Paso Robles, CA 93447PAGE 2 OF 12
Telephone: (800) 350-2223Fax: (805) 238-4201Page Rev. Date: 07-31-07
NP231 SHORT SHAFT "FIXED YOKE" KIT
INSTALLATION PROCEDURES:
Every effort has been made to make sure your kit fits and works right the first time. However, if you happen to
experience a problem with your kit, please contact us by our toll free
technical assistance line at (800)350-2223, Monday through Friday
8:00 a.m. to 4:00 p.m. PST.
The installation of this kit requires you to nearly disassemble
the entire transfer case. If your transfer case is in need
of a rebuild, now is the perfect time to do it. To install this
kit, it is easier to remove your transfer case and set it on
end upon a workbench, but it is not necessary.
Here are a couple of points to keep in mind that will make the
installation much easier if you've never disassembled a New
Process transfer case:
1. Keep all bolts, nuts, washers, etc. separated into groups as you remove
them. Make sure you keep them in a labeled container that indicates what part of the transfer case they came from.
2. Keep all small parts in separate containers and label as to location and origin.
3. Make sure you have plenty of time and a clean, spacious area to perform the installation.
THINGS TO CONSIDER BEFORE YOU BEGIN:
1. This kit is shipped with a rear 1310 series C.V. type yoke. You will need a C.V. equipped driveshaft. We do also
offer other yoke options. P/N 300369 is a 1330CV yoke that uses the same seal as the 1310CV yoke provided
in this kit. P/N 716295 - 1310 non CV yoke, P/N 300472 - 1350 non CV yoke, P/N 300473 - 1410 non CV yoke,
P/N 300470 - 1300 series flange yoke, and P/N 300471 - 1410 non CV flange yoke. These yokes can also be used
on our fixed yoke kit as long as the tailhousing seal is changed. The seal required is our P/N 716755 or a CR seal
P/N 21061.
2. Medium strength threadlocker is recommended on all threaded fasteners.
3. A sealant such as RTV, (like the OEM sealant) is needed and is available from your local Jeep/Dodge dealer.
P/N 82300234.
4. The shift rail on the New Process transfer case may require shortening. Please refer to Page 9 of these instructions
to verify. If your transfer case requires this modification, then it can be done as described on Page 9 or the rail
can be removed from the case and modified while the case is disassembled. If the rail is going to be removed
and modified, please take note to how this mechanism is installed into the case assembly.
SPECIAL NOTE:The components packaged in this kit have been assembled and machined for specific type of conversions. Modifications to any of the
components will void any possible warranty or return privileges. If you do not fully understand modifications or changes that will be required to complete your conversion,
we strongly recommend that you contact our sales department for more information. This instruction sheet is only to be used for the assembly of Advance Adapter
components. We recommend that a service manual pertaining to your vehicle be obtained for specific torque values, wiring diagrams and other related equipment.
These manuals are normally available at automotive dealerships and parts stores.
P.O. Box 247, 4320 Aerotech Center WayNew Item: (12/98)
Paso Robles, CA 93447PAGE 3 OF 12
Telephone: (800) 350-2223Fax: (805) 238-4201Page Rev. Date: 07-31-07
NP231 SHORT SHAFT "FIXED YOKE" KIT
DRIVE SHAFT MODIFICATION:
This job should be performed by a local driveline repair shop capable of balancing the finished assembly. (Use a C.V.
joint & long slip spline style shaft assembly.)
With the vehicle finished and on the ground, measure a straight line between the transfer case output yoke and the rear
pinion yoke center mating flanges. (Fig. A)
(Fig. A)
For proper C.V. type drive shaft operation, the rear differential should be pointed at the transfer case output yoke under
normal driving load.
If install is performed on jack stands, make sure you have supported the vehicle well!
Place the transfer case range selector in the 4L position.
Remove front & rear drive shafts and begin at the disassembly procedures. (Step 1, Fig. 1)
SPECIAL NOTE:The components packaged in this kit have been assembled and machined for specific type of conversions. Modifications to any of the
components will void any possible warranty or return privileges. If you do not fully understand modifications or changes that will be required to complete your conversion,
we strongly recommend that you contact our sales department for more information. This instruction sheet is only to be used for the assembly of Advance Adapter
components. We recommend that a service manual pertaining to your vehicle be obtained for specific torque values, wiring diagrams and other related equipment.
These manuals are normally available at automotive dealerships and parts stores.
P.O. Box 247, 4320 Aerotech Center WayNew Item: (12/98)
Paso Robles, CA 93447PAGE 4 OF 12
Telephone: (800) 350-2223Fax: (805) 238-4201Page Rev. Date: 07-31-07
NP231 SHORT SHAFT "FIXED YOKE" KIT
DISASSEMBLY
(Fig. 1) Yoke Nut Removal
(1) Remove Speed-o-drive.
(2) Remove front yoke nut.
(a) Move range lever to 4L position.
(b) Remove front yoke nut with 1-1/8" socket using an impact
wrench. (Fig. 1)
(3) Remove yoke.
(Discard seal washer).
(4) Remove selector lever.(Fig. 2)
Note: If difficult, use a puller.
(Fig. 3) Slinger Removed / Harmonic Dampener
(5) Remove the output shaft boot. Spread band clamps with a Awl.
Slide boot off.
(6) Remove slinger (this one is tough)! Good thing you won't need
this later. (Fig. 3)
(6a) On newer transfer cases, Jeep used a harmonic dampener. The
dampener has 3 tapped metric holes (6mm-1.00). By installing
bolts into these holes, they will go through the dampener and
press against the stock tailhousing, pressing the harmonic
dampener off the output shaft.
(7) Remove stop spacer & snap ring. (Fig. 4)
(Fig. 2) Range Selector Removal
SPECIAL NOTE:The components packaged in this kit have been assembled and machined for specific type of conversions. Modifications to any of the
components will void any possible warranty or return privileges. If you do not fully understand modifications or changes that will be required to complete your conversion,
we strongly recommend that you contact our sales department for more information. This instruction sheet is only to be used for the assembly of Advance Adapter
components. We recommend that a service manual pertaining to your vehicle be obtained for specific torque values, wiring diagrams and other related equipment.
These manuals are normally available at automotive dealerships and parts stores.
(10) Remove tailhousing bolts with 10mm socket & remove
tailhousing. (Fig. 8)
SPECIAL NOTE:The components packaged in this kit have been assembled and machined for specific type of conversions. Modifications to any of the
components will void any possible warranty or return privileges. If you do not fully understand modifications or changes that will be required to complete your conversion,
we strongly recommend that you contact our sales department for more information. This instruction sheet is only to be used for the assembly of Advance Adapter
components. We recommend that a service manual pertaining to your vehicle be obtained for specific torque values, wiring diagrams and other related equipment.
These manuals are normally available at automotive dealerships and parts stores.
P.O. Box 247, 4320 Aerotech Center WayNew Item: (12/98)
Paso Robles, CA 93447PAGE 6 OF 12
Telephone: (800) 350-2223Fax: (805) 238-4201Page Rev. Date: 07-31-07
NP231 SHORT SHAFT "FIXED YOKE" KIT
(Fig. 11) Front Drive Chain & Shaft Removal
(Fig. 9) Rear Case Half Removal
(11) Remove the rear case bolts. A 10mm 12 pt. socket is needed
for the spline head bolt and a 15mm socket for the remaining
bolts. NOTE: The two black oxide finished bolts are located at
the case dowel positions and require a washer under them.
(12) Start to remove the rear case from the front case by inserting
pry bars at the cast-in locations ONLY! (Fig. 9)
(a) Pry apart evenly to break the sealer bead along the case
mating surfaces.
(13) (Fig. 10)
back of the case until the back half of the case has been taken
off far enough to disengage the pump drive splines on the stock
output shaft. At that time, you can either slide the pump up on
the housing and remove the pump pickup tube or just remove the
pump and pickup tube complete with the rear case half.
(a) Inspect the pickup tube "o-ring" in the pump and replace if
(b) Remove, clean and inspect the inner case for wear.
The oil pump pickup tube is not accessible from the
needed. The same goes for the front shaft seal in the pump.
Do NOT disassemble the pump; it is not a serviceable item.
(14) Front output shaft removal:
(a) Pull the front output shaft out of the front bearing. (Fig. 11)
(b) Slide drive chain off the rear output shaft and remove both
shaft and chain for cleaning & inspection.
(15) Rear output shaft removal:
(a) Grasp the main shaft and remove the shaft, drive sprocket
and mode hub assembly.
(Fig. 12) Front Drive Chain & Shaft Removal
(16) Output shaft disassembly:
(a) Remove the mode hub retaining ring with heavy duty snap
ring pliers. (Fig. 12)
(b) Slide remaining components, mode hub & drive sprocket off
shaft.
(17) This is as far into the case you need to go unless you find foreign
(Fig. 10) Oil Pump Removal
SPECIAL NOTE:The components packaged in this kit have been assembled and machined for specific type of conversions. Modifications to any of the
components will void any possible warranty or return privileges. If you do not fully understand modifications or changes that will be required to complete your conversion,
we strongly recommend that you contact our sales department for more information. This instruction sheet is only to be used for the assembly of Advance Adapter
components. We recommend that a service manual pertaining to your vehicle be obtained for specific torque values, wiring diagrams and other related equipment.
These manuals are normally available at automotive dealerships and parts stores.
material inside usually caused by a worn or stretched drive
chain. You will need to be the judge.
P.O. Box 247, 4320 Aerotech Center WayNew Item: (12/98)
Paso Robles, CA 93447PAGE 7 OF 12
Telephone: (800) 350-2223Fax: (805) 238-4201Page Rev. Date: 07-31-07
NP231 SHORT SHAFT "FIXED YOKE" KIT
New Process 231 transfer cases have used two types or styles of output shafts. The current style New Process output
shaft started to be used in 1997 and is still being used. This newer style shaft eliminated the caged needle bearings in the
drive sprocket.
We have designed our Heavy Duty fixed yoke output shaft kit with the most current design shaft found in the New Process
231 transfer case. Our shaft looks like the shaft below left - listed as "TJ" style. Jeeps having the earlier style output
shaft, listed as "YJ" style, can use this kit by simply removing the caged needle bearing from the stock drive sprocket.
TJ style shaft q
Current NP231 shaft design
and our kit design. No needle
bearings required.
SPECIAL NOTE:The components packaged in this kit have been assembled and machined for specific type of conversions. Modifications to any of the
components will void any possible warranty or return privileges. If you do not fully understand modifications or changes that will be required to complete your conversion,
we strongly recommend that you contact our sales department for more information. This instruction sheet is only to be used for the assembly of Advance Adapter
components. We recommend that a service manual pertaining to your vehicle be obtained for specific torque values, wiring diagrams and other related equipment.
These manuals are normally available at automotive dealerships and parts stores.
P.O. Box 247, 4320 Aerotech Center WayNew Item: (12/98)
Paso Robles, CA 93447PAGE 8 OF 12
Telephone: (800) 350-2223Fax: (805) 238-4201Page Rev. Date: 07-31-07
NP231 SHORT SHAFT "FIXED YOKE" KIT
New Shaft
ASSEMBLY CONSIDERATIONS
(Fig. 1A) Drive Sprocket Needle Bearings
(1) These bearings must be removed. Once the bearings are
removed, clean the inside of the drive gear to make sure it is free
of any type of debris.
On 1997 and newer transfer cases, the drive sprocket
does not use caged needle bearings. If you have this
newer style, then continue on to Fig. 3A (2).
(Fig. 2A) Pull the Needle Bearings Out
(Fig. 3A) New Main Output Shaft Assembly
(2) Main shaft assembly:
(a) Clean all components.
(b) Prelube all components with a quality assembly lubricant.
(Fig. 3A)
(c) Slide drive sprocket into position.
(d) Slide mode hub into position.
(e) Install the retaining ring into position after the mode hub.
(Fig. 4A)
(Fig. 4A) (Large) Retaining Ring Installation
CONTINUE TO PAGE 9
SPECIAL NOTE:The components packaged in this kit have been assembled and machined for specific type of conversions. Modifications to any of the
components will void any possible warranty or return privileges. If you do not fully understand modifications or changes that will be required to complete your conversion,
we strongly recommend that you contact our sales department for more information. This instruction sheet is only to be used for the assembly of Advance Adapter
components. We recommend that a service manual pertaining to your vehicle be obtained for specific torque values, wiring diagrams and other related equipment.
These manuals are normally available at automotive dealerships and parts stores.
P.O. Box 247, 4320 Aerotech Center WayNew Item: (12/98)
Paso Robles, CA 93447PAGE 9 OF 12
Telephone: (800) 350-2223Fax: (805) 238-4201Page Rev. Date: 07-31-07
NP231 SHORT SHAFT "FIXED YOKE" KIT
(Fig. 5A) New Main Output Shaft Assembly
(3) Output shaft and drive chain assembly:
(a) Lubricate chain & shaft with ATF.
(b) Insert main shaft assembly into the housed planetary
assembly.
(c) Install the drive chain onto the front output shaft.
(d) Insert them into the bearing. Lift upward and tilt the shaft
toward the main shaft to work the chain into position.
(Fig. 5A)
(4) Make sure the mode spring is in place, seen in the middle.
(Fig. 5A)
(Fig. 7A) Thin film RTV Applied Prior to Mating
Case Halves.
(Fig. 6A) Case Half Pre-assembly
(5) Rear case assembly:
(a) With all components clean, install oil pump.
(b) Seat the pickup tube into the pump "o-ring". (Fig. 6A)
(c) Prelube the front output shaft bearing located in the rear
case.
(6) Apply a thin film of sealant to the front case. Use a good RTV,
like the OEM sealant, available from your local Jeep dealer.
(Fig. 7A) P/N = 82300234.
SPECIAL NOTE:The components packaged in this kit have been assembled and machined for specific type of conversions. Modifications to any of the
components will void any possible warranty or return privileges. If you do not fully understand modifications or changes that will be required to complete your conversion,
we strongly recommend that you contact our sales department for more information. This instruction sheet is only to be used for the assembly of Advance Adapter
components. We recommend that a service manual pertaining to your vehicle be obtained for specific torque values, wiring diagrams and other related equipment.
These manuals are normally available at automotive dealerships and parts stores.
(7) Assembly of case halves: (Fig. 8A)
(Fig. 8A) Case Halves Assembled
(a) Slide the pump & case into position.
(b) If you have difficulty, check for possible problems. DO NOT
FORCE! Mode fork rail extends through rear case!
(c) Install all fasteners in their original positions. (Black bolts
P.O. Box 247, 4320 Aerotech Center WayNew Item: (12/98)
Paso Robles, CA 93447PAGE 10 OF 12
Telephone: (800) 350-2223Fax: (805) 238-4201Page Rev. Date: 07-31-07
NP231 SHORT SHAFT "FIXED YOKE" KIT
(Fig. 9A) Speed-o- Ring Gear Install
(8) Assemble speed-o-drive
(a) Install retaining ring, located just behind the pump.
(b) Slide ring gear into position.
(c) Install retaining ring behind ring gear. (Fig. 9A)
NOTE: On some NP231 transfer cases, the shift rail must be shortened.
This shift rail protrudes out of the transfer case and goes into the
tailhousing. The new tailhousing has a pocket depth of 1.125".
Shift your transfer case into 4WD so the shift rod is protruding the
furthest out of the transfer case. If this shifter rod protrudes more than
1" out of the back side of the transfer case, then the shift rail must be
shortened. Ideally the shift rod should protrude exactly 1".
Transfer cases that will normally require this rail to be shortened
measure 1.5" (photo above left).
Using a hack saw or cutoff wheel (and safety glasses), trim the shift
rail shaft so that it protrudes only 1" (photo above right).
This kit is designed for both the Cherokees and Wranglers. The
Cherokees use a vacuum actuator on the New Process tailhousing; our
casting has this provision. On Wranglers, this threaded hole must be
plugged. We have provided a plug and washer for this purpose. We
also recommend that you use a bit of silicone to properly seal the plug.
(Fig. 10A) Bearing Installed
and Retained with the 716464
Snap Ring
(10) Short Tailhousing Installation:
(a) Prelube bearing & seal in new short tailhousing assembly.
(Fig. 11A)
(b) Apply sealant to tailhousing, mating surface of rear case.
(thin film)
(c) While supporting main shaft, slide new tail assembly into
position.
(d) Use care when indexing pump outer tabs and aligning tail
assembly for installation. (Fig. 12A) NOTE: Pull back on
the output shaft to seat it against the rear bearing.
(e) Install the (5) 10mm bolts that retain the tailhousing and
torque evenly to 20-27 N.m (15-20 ft./lbs.)
(Fig. 12A) Tailhousing Installation
(Fig. 11A) Seal
Installed
SPECIAL NOTE:The components packaged in this kit have been assembled and machined for specific type of conversions. Modifications to any of the
components will void any possible warranty or return privileges. If you do not fully understand modifications or changes that will be required to complete your conversion,
we strongly recommend that you contact our sales department for more information. This instruction sheet is only to be used for the assembly of Advance Adapter
components. We recommend that a service manual pertaining to your vehicle be obtained for specific torque values, wiring diagrams and other related equipment.
These manuals are normally available at automotive dealerships and parts stores.
P.O. Box 247, 4320 Aerotech Center WayNew Item: (12/98)
Paso Robles, CA 93447PAGE 11 OF 12
Telephone: (800) 350-2223Fax: (805) 238-4201Page Rev. Date: 07-31-07
NP231 SHORT SHAFT "FIXED YOKE" KIT
(Figures 13A) Final Installation
(11) Yoke & Seal Washer installation: (This will apply to both Front & Rear yoke assembly)
(a) Slide the yoke seal into position on the shaft thread.
(b) Lube the yoke as well as the seal with ATF.
(c) A little trick to keep the spline seal in good shape is to slide the yoke half way on and walk the yoke into position
with the retaining nut. Torque to 140-150 ft./lbs. with 1-1/8" socket.
(d) Install your stock speedometer housing into the new tailhousing. Depending on which speedometer gear (tooth
count) you are using will determine the proper rotation of the speedometer housing. Each housing has 4 possible
rotation options. Identify you speedometer gear tooth count and locate that tooth count on your speedometer
housing. The number range on your housing will need to be lined up with the housing retaining clip (see photo).
A touch of RTV Blue silicon around the "o"-ring will help seal the housing to the tailhousing.
(12) Fill to recommended level with ATF.
(13) Reconnect all exterior items: driveshafts, 4WD switch, speedometer cable, etc.
(14) Happy Trails!
SPECIAL NOTE:The components packaged in this kit have been assembled and machined for specific type of conversions. Modifications to any of the
components will void any possible warranty or return privileges. If you do not fully understand modifications or changes that will be required to complete your conversion,
we strongly recommend that you contact our sales department for more information. This instruction sheet is only to be used for the assembly of Advance Adapter
components. We recommend that a service manual pertaining to your vehicle be obtained for specific torque values, wiring diagrams and other related equipment.
These manuals are normally available at automotive dealerships and parts stores.
P.O. Box 247, 4320 Aerotech Center WayNew Item: (12/98)
Paso Robles, CA 93447PAGE 12 OF 12
Telephone: (800) 350-2223Fax: (805) 238-4201Page Rev. Date: 07-31-07
If you have not changed your tire size or your axles, your stock speedometer drive gear will remain the same.
However, if a new axle ratio and/or tire size is used, see Fig. A & B. These new speedometer drive gears
can be purchased at your local Jeep dealership.
When installing a speedometer gear with either 39, 40, 41 or 42 teeth,
the gear and the housing must be installed separately. These are all
large diameter speedometer gears. By first installing the gear into the
tailhousing you will be able to tilt the gear shaft up allowing you to
position the gear past the Atlas output shaft. Once this gear is in place,
the speedometer housing must be aligned with the speedometer
gear shaft and indexed into the tailhousing. When installing the
speedometer housing, lube the o-ring that contacts the Atlas
tailhousing with a bit of Torco oil. This will prevent the o-ring from being
nicked upon installation or rotation, causing this housing to leak.
SPECIAL NOTE:The components packaged in this kit have been assembled and
machined for specific type of conversions. Modifications to any of the components will
void any possible warranty or return privileges. If you do not fully understand modifications
or changes that will be required to complete your conversion, we strongly recommend that
you contact our sales department for more information. This instruction sheet is only
to be used for the assembly of Advance Adapter components. We recommend that a service
manual pertaining to your vehicle be obtained for specific torque values, wiring diagrams
and other related equipment. These manuals are normally available at automotive
dealerships and parts stores.