1994 JEEP CHEROKEE Service Repair Manual

²Outer diameter of bearing is 46.8 mm (1.844 in.)
and inside diameter is 26.0 mm (1.024 in.).
(60) Coat tabbed thrust race with petroleum jelly
and install it on planetary gear (Fig. 48). Race outer
diameter is 41.8 mm (1.646 in.) and inside diameter
is 27.1 mm (1.067 in.).
(61) Install assembled overdrive planetary gear
and clutch (Fig. 49).
(62) Coat thrust bearing and race assembly with
petroleum jelly and install it on clutch input shaft
(Fig. 50). Bearing and race outer diameter is 50.2
mm (1.976 in.) and inside diameter is 28.9 mm (1.138
in.).
(63) Install overdrive brake pack as follows:
(a) Install 4.0 mm (0.157 in.) thick plate first.
Rounded edge of plate must face upward.(b) Install a disc followed by a plate until the re-
quired number of discs and plates are installed. Be
sure to install the stepped plate last with the flat
side of the plate facing the disc (Fig. 51).
(c) Confirm that four discs and three plates have
been installed.
(64) Install clutch pack snap ring (Fig. 52).
(65) Coat thrust bearing race with petroleum jelly
and install it in oil pump (Fig. 53). Bearing race
Fig. 47 Installing Ring Gear Thrust Bearing And
Race
Fig. 48 Installing Planetary thrust Race
Fig. 49 Installing Overdrive Planetary And Clutch
Assembly
Fig. 50 Installing Input Shaft Thrust Bearing And
Race Assembly
21 - 266 AW-4 TRANSMISSION OVERHAULJ

outer diameter is 47.2 mm (1.858 in.) and inside di-
ameter is 28.1 mm (1.106 in.).
(66) Lubricate and install replacement O-ring on
oil pump body.
(67) Install oil pump in case. Align pump and case
bolt holes and carefully ease pump into place (Fig.
54).
CAUTION: Do not use force to seat the pump. The
seal rings on the stator shaft could be damaged if
they bind or stick to the direct clutch drum.
(68) Tighten oil pump bolts to 22 Nzm (16 ft. lbs.)
torque.
(69) Verify input shaft rotation. Shaft should rotate
smoothly and not bind.(70) Lubricate and install new O-ring on transmis-
sion throttle cable adapter and install cable in case
(Fig. 55).
(71) Check clutch and brake operation. Operate
clutches and brakes with compressed air applied
through feed holes in case (Fig. 56). Listen for clutch
and brake application. If you do not hear a clutch or
brake apply, disassemble transmission and repair
fault before proceeding.It is necessary to block
the overdrive clutch accumulator feed hole No.
8 (Fig. 56) in order to check direct clutch oper-
ation.
(72) Lubricate and install new O-rings on accumu-
lator pistons (Fig. 57).
(73) Assemble and install accumulator pistons and
springs (Fig. 57).
Fig. 53 Installing Oil Pump Thrust Race
Fig. 54 Installing Oil Pump
Fig. 51 Installing Overdrive Clutch Pack
Fig. 52 Installing Clutch Pack Snap Ring
JAW-4 TRANSMISSION OVERHAUL 21 - 267

(74) Install new check ball body and spring (Fig.
58).
(75) Position valve body on case (Fig. 59).
(76) Install detent spring (Fig. 59).
(77) Align manual valve, detent spring and shift
sector (Fig. 59).
(78) Connect transmission throttle cable to throttle
valve cam (Fig. 60).
(79) Install and tighten valve body-to-case bolts to
10 Nzm (7 ft. lbs.) torque.(80) Connect valve body solenoid wires to solenoids
(Fig. 61).
(81) Install new O-ring on solenoid harness
adapter and secure adapter to case.
Fig. 57 Accumulator Piston And Spring Installation
Fig. 58 Installing Check Ball Body And Spring
Fig. 55 Installing Transmission Throttle Cable
Fig. 56 Clutch And Brake Feed Hole Locations
21 - 268 AW-4 TRANSMISSION OVERHAULJ

(82) Install valve body oil tubes (Fig. 62). Tap
tubes into place with a plastic mallet. Be sure the
flanged tube ends and straight tube ends are in-
stalled as shown.
(83) Install new gaskets on oil screen and install
screen on valve body. Tighten screen bolts to 10 Nzm
(7 ft. lbs.) torque.
(84) Install magnet in oil pan. Be sure magnet
does not interfere with valve body oil tubes.
(85) Apply Mopar or Loctite 599 to sealing surface
of oil pan. Sealer bead should be at least 3 mm (1/8
in.) wide. Install pan on case and tighten pan bolts to
7Nzm (65 in. lbs.) torque.
(86) Install transmission speed sensor rotor and
key on output shaft (Fig. 63).
Fig. 63 Installing Transmission Speed Sensor Rotor
And Key
Fig. 61 Connecting Valve Body Solenoid Wires
Fig. 62 Installing Valve Body Oil Tubes
Fig. 59 Aligning Manual Valve, Shift Sector And
Detent Spring
Fig. 60 Connecting Transmission Throttle Cable
JAW-4 TRANSMISSION OVERHAUL 21 - 269

(87) Install spacer and speedometer drive gear on
output shaft. Then install retaining snap ring (Fig.
64).
(88) Apply bead of Mopar or Loctite 599 sealer to
sealing surface at rear of case (Fig. 65).
(89) Install adapter housing on transmission.
Tighten adapter bolts to 34 Nzm (25 ft. lbs.) torque.
(90) Install transmission speed sensor (Fig. 66).
Tighten sensor bolt to 7.4 Nzm (65 in. lbs.) torque
and connect sensor wire harness connector.
(91) Install converter housing (Fig. 67). Tighten 12
mm diameter housing bolts to 57 Nzm (42 ft. lbs.)
torque. Tighten 10 mm diameter housing bolts to 34
Nzm (25 ft. lbs.) torque.(92) Install transmission shift lever on manual
valve shaft. Do not install lever attaching nut at this
time.
(93) Move transmission shift lever fully rearward.
Then move lever two detent positions forward.
(94) Mount park/neutral position switch on manual
valve shaft and tighten switch adjusting bolt just
enough to keep switch from moving (Fig. 68).
(95) Install park/neutral position switch tabbed
washer and retaining nut (Fig. 68). Tighten nut to
6.9 Nzm (61 in. lbs.) torque, but do not bend any of
the washer tabs against the nut at this time.
(96) Align park/neutral position switch standard
line with groove or flat on manual shaft (Fig. 68).
(97) Tighten park/neutral position switch adjusting
bolt to 13 Nzm (9 ft. lbs.) torque.
(98) Install transmission shift lever on manual
Fig. 66 Installing Transmission Speed Sensor
Fig. 67 Installing Converter Housing
Fig. 64 Installing Spacer And Speedometer Drive
Gear
Fig. 65 Applying Sealer To Case Rear Flange
21 - 270 AW-4 TRANSMISSION OVERHAULJ

valve shaft. Tighten lever attaching nut to 16 Nzm
(12 ft. lbs.) torque.
(99) Install retaining clamp for wire harness and
throttle cable (Fig. 69).
(100) Install torque converter.
(101) Verify that converter is seated by measuring
distance between converter housing flange and one of
the converter mounting pads (Fig. 70). Use straight-
edge and vernier calipers to measure distance. On 6-
cyl. transmissions, distance should be 16.5 mm (0.650
in.).
(102) Secure converter in transmission with C-
clamp or metal strapping. Do this before mounting
transmission on jack or moving transmission under
vehicle.
(103) Install lower half of transmission fill tube (in-
stall upper half after transmission is in vehicle).
CAUTION: The transmission cooler and lines must
be reverse flushed if overhaul corrected a malfunc-
tion that generated sludge, metal particles, or
clutch friction material. The torque converter should
also be replaced if contaminated by the same mal-
function. Debris and residue not flushed from the
cooler and lines will flow back into the transmissionand converter. The result will be a repeat failure and
shop comeback.Fig. 69 Installing Cable/Harness Clamps
Fig. 70 Checking Converter Installation
Fig. 68 Park/Neutral Position Switch Installation/
Adjustment
JAW-4 TRANSMISSION OVERHAUL 21 - 271

NP231 TRANSFER CASE
INDEX
page page
General Information...................... 272
Shift Linkage Adjustment.................. 275
Speedometer Service.................... 275
Transfer Case Assembly.................. 282
Transfer Case Disassembly and Overhaul..... 277Transfer Case Identification................ 273
Transfer Case Installation................. 276
Transfer Case Lubricant.................. 273
Transfer Case Removal................... 276
GENERAL INFORMATION
The NP231 is a part-time transfer case with a low
range reduction gear system (Fig. 1). The NP231 has
three operating ranges plus a Neutral position. A low
range system provides a reduction ratio for increased
low speed torque capability.The NP231 is the Command Trac transfer case. It
is used in XJ and YJ models.
Two versions of the NP231 are used. One version
retains the synchronizer components used in previ-
ous models. A newly introduced version is not
equipped with synchro components.
Fig. 1 NP231 Transfer Case
21 - 272 NP231 TRANSFER CASEJ

OPERATING RANGES
NP231 operating ranges are: 2-wheel drive high; 4-
wheel drive high and 4-wheel drive low (Fig. 2).
2-wheel drive range is for use on all surfaces. The
4-wheel drive high and low ranges are undifferenti-
ated and should only be used on unpaved, low trac-
tion surfaces only.
SHIFT MECHANISM
Operating ranges are selected with a floor mounted
shift lever. The shift lever is connected to the trans-
fer case range lever by an adjustable linkage rod. A
straight line shift pattern is used (Fig. 2). Range po-
sitions are marked on the shifter bezel cover plate. A
front axle disconnect mechanism is only used on cer-
tain models.
TRANSFER CASE IDENTIFICATION
A circular ID tag is attached to the rear case of
each NP231 transfer case (Fig. 3). The ID tag pro-vides the transfer case model number, assembly
number, serial number and low range ratio.
The transfer case serial number also represents the
date of build. For example, a serial number of 8-
10-92 would represent August 10, 1992.
TRANSFER CASE LUBRICANT
Recommended Lubricant
Use Mopar Dexron II, or ATF Plus, type 7176 au-
tomatic transmission fluid in the NP231 transfer
case.
Lubricant Capacity
Approximate refill lubricant capacity is 1.54 liters
(3.25 pints) for YJ and 1.04 liters (2.2 pints) for XJ.
Fill Level
The correct fill level is to the bottom edge of the fill
plug hole. The vehicle must be level in order to en-
sure an accurate fluid level check.
Fig. 2 NP231 Shift Pattern
Fig. 3 Transfer Case Identification Tag
JNP231 TRANSFER CASE 21 - 273