TRANSFER CASE - NV231

DESCRIPTION
OPERATION
DIAGNOSIS AND TESTING - TRANSFER CASE - NV231
REMOVAL
DISASSEMBLY
CLEANING
INSPECTION
ASSEMBLY
INSTALLATION

DESCRIPTION

The NV231 is a part-time transfer case with a low range reduction gear system. The NV231 has three operating ranges plus a NEUTRAL position. A low range system provides a reduction ratio for increased low speed torque capability.

The geartrain is mounted in two aluminum case halves attached with bolts. The mainshaft front and rear bearings are mounted in aluminum retainer housings bolted to the case halves.

OPERATING RANGES

Transfer case operating ranges are:

2WD (2-wheel drive)
4Hi (4-wheel drive)
4 Lo (4-wheel drive low range)

The 2WD range is for use on any road surface at any time.

The 4Hi and 4 Lo ranges are for off road use only. They are not for use on hard surface roads. The only exception being when the road surface is wet or slippery or covered by ice and snow.

The low range reduction gear system is operative in 4 Lo range only. This range is for extra pulling power in off road situations. Low range reduction ratio is 2.72:1.

SHIFT MECHANISM

Operating ranges are selected with a floor mounted shift lever. The shift lever is connected to the transfer case range lever by a shift cable. A straight line shift pattern is used. Range positions are marked on the shifter knob bezel.

IDENTIFICATION

A circular ID tag (1) is attached to the rear case of each transfer case. The ID tag provides the transfer case model number, assembly number, serial number, and low range ratio.

The transfer case serial number also represents the date of build.

OPERATION

The input gear is splined to the transmission output shaft. The input gear drives the mainshaft through the planetary assembly and range hub. The front output shaft is operated by a drive chain that connects the shaft to a drive sprocket on the mainshaft. The drive sprocket is engaged/disengaged by the mode fork, which operates the mode sleeve and hub. The sleeve and hub are not equipped with a synchronizer mechanism for shifting.

DIAGNOSIS AND TESTING - TRANSFER CASE - NV231

DIAGNOSIS CHART

Condition	Possible Cause	Correction
Transfer case difficult to shift or will not shift into desired range.	1) Vehicle speed too great to permit shifting.	1) Slow vehicle and shift into desired range.
	2) If vehicle was operated for an extended period in 4H mode on dry surface, driveline torque load may cause difficulty.	2) Stop vehicle and shift transfer case to Neutral position. Transfer case can then be shifted to the desired mode.
	3) Transfer case shift cable binding.	3) Repair or replace cable as necessary.
	4) Insufficient or incorrect lubricant.	4) Drain and refill transfer case with the correct type and quantity of lubricant.
	5) Internal transfer case components binding, worn, or damaged.	5) Repair or replace components as necessary.
Transfer case noisy in all drive modes.	1) Insufficient or incorrect lubricant.	1) Drain and refill transfer case with the correct type and quantity of lubricant.
Transfer case noisy while in, or jumps out of, 4L mode.	1) Transfer case not completely engaged in 4L position.	1) Slow vehicle, shift transfer case to the Neutral position, and then shift into the 4L mode.
	2) Transfer case shifter binding.	2) Repair, replace, or tighten shifter as necessary.
	3) Range fork damaged, inserts worn, or fork is binding on the shift rail.	3) Repair or replace components as necessary.
	4) Low range gear worn or damaged.	4) Repair or replace components as necessary.
Lubricant leaking from transfer case seals or vent.	1) Transfer case overfilled.	1) Drain lubricant to the correct level.
	2) Transfer case vent closed or restricted.	2) Clean or replace vent as necessary.
	3) Transfer case seals damaged or installed incorrectly.	3) Replace suspect seal.
Abnormal tire wear.	1) Extended operation in 4Hi mode on dry surfaces,	1) Operate vehicle in 2H mode on dry surfaces.

REMOVAL

1. Shift transfer case into NEUTRAL.
2. Raise vehicle.
3. Remove skid plate (1).

4. Drain transfer case lubricant.
5. Mark front and rear propeller shaft yokes for alignment reference.
6. Disconnect front/rear propeller shafts at transfer case.
7. Disconnect transfer case position sensor connector (1).

8. Disconnect transfer case shift cable (2) at the range lever.
9. Disconnect the transfer case shift cable from the shift cable bracket.

10. Disconnect transfer case vent hose (3).
11. Support transfer case with transmission jack.
12. Secure transfer case to jack with chains.
13. Remove nuts attaching transfer case to transmission.
14. Pull transfer case and jack rearward to disengage transfer case.
15. Remove transfer case from under vehicle.

DISASSEMBLY

Position transfer case on shallow drain pan. Remove drain plug and drain lubricant remaining in case.

REAR RETAINER AND OIL PUMP

1. Spread band clamp which holds output shaft boot to the output shaft slinger with a suitable awl, or equivalent.
2. Remove output shaft boot from slinger and output shaft.
3. Remove the output shaft rear slinger (3) using Puller MD-998056-A (2).

4. Use a suitable pry tool, or a slide hammer mounted screw, to remove the seal (2) from the rear retainer (1).

5. Remove the rear output bearing I.D. retaining ring (2).
6. Remove the bolts holding the rear retainer to the rear case half.

7. Tap rear retainer with rawhide or rubber mallet to loosen sealer bead.
8. Remove rear retainer (2) from rear case half.

9. Remove the remaining output shaft bearing snap-ring.
10. Disengage oil pickup tube from oil pump (1) and remove oil pump assembly. Remove oil pump by tilting the edge of the oil pump from under the edge of the rear case half and sliding the pump off the output shaft.

11. Remove pick-up tube o-ring (2) from oil pump (1), if necessary. Do not disassemble the oil pump, it is not serviceable.

COMPANION FLANGE AND RANGE LEVER

1. Remove transfer case position sensor (1).

2. Install two bolts (2) partially into the propeller shaft companion flange (3), 180° from each other.
3. Install the rectangular end of the Flange Holder C-3281 (1) over the bolts to hold the companion flange stationary and remove the nut holding the companion flange to the output shaft.

4. Use Remover C-452 (3) to remove the companion flange (2).

NOTE: Be sure to note the orientation of the range lever (lever up or down) so that it may be re-installed in the same direction.

5. Remove seal washer from front output shaft. Discard washer as it should not be reused.
6. Remove the bolt (2) that attaches the range lever (1) to sector shaft. Then move sector to neutral position and remove range lever from shaft.

CLEANING

Clean the transfer case parts with a standard parts cleaning solvent. Remove all traces of sealer from the cases and retainers with a scraper and 3M™ all purpose cleaner. Use compressed air to remove solvent residue from oil feed passages in the case halves, retainers, gears, and shafts.

INSPECTION

MAINSHAFT/SPROCKET/HUB

Inspect the splines on the hub (1) and shaft (3) and the teeth on the sprocket (2). Minor nicks and scratches can be smoothed with an oilstone. However, replace any part that is damaged.

Check the contact surfaces in the sprocket bore and on the mainshaft. Minor nicks and scratches can be smoothed with 320-400 grit emery cloth but do not try to salvage the shaft if nicks or wear is severe.

INPUT GEAR AND PLANETARY CARRIER

Input Gear And Carrier Components

1 - PLANETARY CARRIER	4 - CARRIER LOCK RING
2 - REAR THRUST WASHER	5 - CARRIER LOCK RETAINING RING
3 - FRONT THRUST WASHER	6 - INPUT GEAR

Check the teeth on the gear (6). Minor nicks can be dressed off with an oilstone but replace the gear if any teeth are broken, cracked, or chipped. The bearing surface on the gear can be smoothed with 300-400 grit emery cloth if necessary.

Examine the carrier body (1) and pinion gears for wear or damage. The carrier will have to be replaced as an assembly if the body, pinion pins, or pinion gears are damaged.

Check the lock ring (4) and both thrust washers (2, 3) for wear or cracks. Replace them if necessary. Also replace the lock retaining ring if bent, distorted, or broken.

SHIFT FORKS/HUBS/SLEEVES

Check condition of the shift forks and mode fork shift rail (2). Minor nicks on the shift rail can be smoothed with 320-400 grit emery cloth.

Inspect the shift fork wear pads (3, 4). The mode fork (2) pads are serviceable and can be replaced if necessary. The range fork (1) pads are not serviceable. The fork must be replaced as an assembly if the pads are worn or damaged.

Check both of the sleeves for wear or damage, especially on the interior teeth. Replace the sleeves if wear or damage is evident.

REAR RETAINER/BEARING/ SEAL/SLINGER/BOOT

Inspect the retainer components. Replace the bearing (8) if rough or noisy. Check the retainer (1) for cracks or wear in the bearing bore. Clean the retainer sealing surfaces with a scraper and 3M™ all purpose cleaner. This will ensure proper adhesion of the sealer during reassembly.

The output shaft slinger and seal (3) should be replaced outright; do not reuse either part.

Replace any part if distorted, bent, or broken. Also replace the boot if cut or torn. Replace the boot band clamps, do not reuse them.

REAR OUTPUT SHAFT/YOKE/DRIVE CHAIN

Check condition of the seal contact surfaces of the yoke slinger (2). This surface must be clean and smooth to ensure proper seal life. Replace the yoke nut and seal washer as neither part should be reused.

Inspect the shaft threads, sprocket teeth, and bearing surfaces. Minor nicks on the teeth can be smoothed with an oilstone. Use 320-400 grit emery to smooth minor scratches on the shaft bearing surfaces. Rough threads on the shaft can be chased if necessary. Replace the shaft if the threads are damaged, bearing surfaces are scored, or if any sprocket teeth are cracked or broken.

Examine the drive chain and shaft bearings. Replace the chain and both sprockets if the chain is stretched, distorted, or if any of the links bind. Replace the bearings if rough, or noisy.

LOW RANGE ANNULUS GEAR

Inspect annulus gear condition carefully. The gear is only serviced as part of the front case. If the gear is damaged, it will be necessary to replace the gear and front case as an assembly. Do not attempt to remove the gear (2)

FRONT/REAR CASES AND FRONT RETAINER

Inspect the cases and retainer for wear and damage. Clean the sealing surfaces with a scraper and 3M™ all purpose cleaner. This will ensure proper sealer adhesion at assembly. Replace the input retainer seal; do not reuse it.

Check case condition. If leaks were a problem, look for gouges and severe scoring of case sealing surfaces. Also make sure the front case mounting studs are in good condition.

Check the front case mounting studs and vent tube. The tube can be secured with Loctite™ 271 or 680 if loose. The stud threads can be cleaned up with a die if necessary. Also check condition of the fill/drain plug threads in the rear case. The threads can be repaired with a thread chaser or tap if necessary. Or the threads can be repaired with Helicoil™ stainless steel inserts if required.

OIL PUMP/OIL PICKUP

Examine the oil pump pickup parts. Replace the pump if any part appears to be worn or damaged. Do not disassemble the pump as individual parts are not available. The pump is only available as a complete assembly. The pickup screen, hose, and tube are the only serviceable parts and are available separately.

ASSEMBLY

Lubricate transfer case components with Mopar® ATF +4, Automatic Transmission Fluid or petroleum jelly (where indicated) during assembly.

BEARINGS AND SEALS

CAUTION: The bearing bores in various transfer case components contain oil feed holes. Make sure replacement bearings do not block the holes.

1. Remove the front output shaft seal (1) from case with pry tool (2).

2. Remove the front output shaft bearing (3) retaining ring (2) with screwdriver (1).

3. Remove bearing with Universal Handle C-4171 (2) and Installer 5065 (3).

4. Install front output shaft front bearing in case with Universal Handle C-4171 (1) and Installer 5064 (2).

5. Install output shaft front bearing retaining ring (1). Start ring into place by hand. Then use small screwdriver to work ring into case groove. Be sure ring is fully seated before proceeding.

6. Install new front output seal in front case with Seal Installer 8143-A (1) as follows:
a. Place new seal on tool. Garter spring on seal goes toward interior of case.
b. Start seal in bore with light taps from hammer. Once seal is started, continue tapping seal into bore until installer tool bottoms against case.

7. Remove the output shaft rear bearing with the screw and jaws from Remover L-4454 (2) and Cup 8148 (3).

8. Install new bearing with Universal Handle C-4171 (1) and Installer 5066 (3).

9. The bearing bore is chamfered at the top. Install the bearing (1) so it is flush with the lower edge of this chamfer (2).

10. Using Remover C-4210 (2) and Universal Handle C-4171 (1), drive input shaft bearing from inside the annulus gear opening in the case .

11. Install locating ring on new bearing.
12. Position case so forward end is facing upward.
13. Using Remover C-4210 and Handle C-4171, drive input shaft bearing (1) into case. The bearing locating ring (1) must be fully seated against case surface.

14. Remove input gear pilot bearing by inserting a suitably sized drift (1) into the splined end of the input gear (2) and driving the bearing out with the drift and a hammer.

15. Install new pilot bearing with Installer 5065 (2) and Handle C-4171 (1).

16. Remove front bearing retainer seal with suitable pry tool.
17. Install new front bearing retainer (1) seal with Installer 7884 (2).

18. Remove seal from oil pump housing with a suitable pry tool
19. Install new seal in oil pump housing with Seal Installer 7888 (2).

20. Remove rear retainer bearing with Installer 8128 and Handle C-4171.
21. Install rear bearing in retainer with Universal Handle C-4171 (1) and Installer 5052 (2).

INPUT AND LOW RANGE GEAR

1. Install first thrust washer (5) in low range gear (3). Be sure washer tabs are properly aligned in gear notches.
2. Install input gear in low range gear (4). Be sure input gear is fully seated.
3. Install remaining thrust washer (5) in low range gear and on top of input gear. Be sure washer tabs are properly aligned in gear notches.
4. Install retainer on input gear and install snap-ring (1).

5. Align and install low range/input gear assembly (2) in front case. Be sure low range gear pinions are engaged in annulus gear (1) and that input gear shaft is fully seated in front bearing.

6. Install snap-ring (2) to hold input/low range gear (1) into front bearing.

7. Clean gasket sealer residue from retainer and inspect retainer for cracks or other damage.
8. Apply a 3 mm (1/8 in.) bead of Mopar® gasket maker or silicone adhesive to sealing surface of retainer.
9. Align cavity in seal retainer with fluid return hole in front of case.

CAUTION: Do not block fluid return cavity on sealing surface of retainer when applying Mopar® gasket maker or silicone adhesive sealer. Seal failure and fluid leak can result.

10. Install bolts to hold retainer (1) to transfer case. Tighten to 21 N·m (16 ft. lbs.) of torque.