Dodge RAM TRUCK 1500 1995 Service Manual page 1559

21 - 278 NP231 HD/NP241/NP241 HD TRANSFER CASE
B R
N P 2 3 1
H 0 / N P 2 4 1 / N P 2 4 1
H D
T R A N S F E R C A S E
INDEX
page
Checking Fluid Level 280
Fluid Drain/Refill 280
General Description 278
In-Vehicle Service 280
Operating Ranges 278
PTO Capability 278
Recommended Lubricant and Capacity 278
Service Diagnosis 280
Shift Linkage Adjustment . 281
Speedometer Service 280
GENERAL DESCRIPTION
The NP231 HD, NP241, and NP241 HD are all
part-time transfer cases with a low-range gear sys­
tem. They provide three operating ranges plus a
Neutral position. The low range position provides a
gear reduction ratio of 2.72:1 for increased low speed
torque capability. Operating ranges , are: 2-high,
4-high and 4-low.
The gear cases, retainer and extension are all of
aluminum. Drive sprockets and an interconnecting
drive chain are used to transmit engine torque to the
front/rear propeller shafts. The mainshaft, input gear
and front output shaft are supported by ball and nee­
dle bearings.
The synchro mechanism consists of a stop ring,
synchro hub with struts and retaining springs and
the sliding clutch (Fig. 1). The synchro components
allow the transfer case to be shifted between 2H and
4H ranges while the vehicle is in motion. However,
the vehicle must be stopped in order to shift into 4L
range.
TRANSFER CASE APPLICATION
The NP231 HD is used in 1500 models only. The
NP241 is used in 2500 models and the NP241 HD is
used in 2500 and 3500 models with a V10 or diesel
engine.
OPERATING RANGES
Transfer case operating ranges are:
• 2WD (2-wheel drive)
@ 4x4 (4-wheel drive)
• 4 Lo (4-wheel drive low range
The 2WD range is for use on any road surface at
any time.
The 4x4 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 covered by
ice and snow.
page
Transfer Case Application 278
Transfer Case Assembly 295
Transfer Case Changes 279
Transfer Case Cleaning and Inspection . . . . . . . . . 293
Transfer Case Disassembly 283
Transfer Case Identification . . . . . . . . . . . . . . . . . 278
Transfer Case Installation . 283
Transfer Case Removal 281
Transfer Case Service 278
Transfer Case Shift Mechanism 279
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 ra­
tio is 2.72:1.
A front axle disconnect system is used to achieve
two-wheel drive mode. The axle disconnect vacuum
motor is actuated by a vacuum switch on the transfer
case. The switch is • operated by the transfer case
range rod.
TRANSFER CASE SERVICE
Overhaul procedures for the NP231 HD and both
versions of the NP241 transfer case are virtually the
same. The only major difference between them being
the PTO gear used in the NP241 HD model.
Although overhaul procedures are the same for all
three transfer cases, internal parts are different and
must not be interchanged.
PTO CAPABILITY
The NP241 HD transfer case has power take-off ca­
pability. A PTO gear permanently attached to the
planetary carrier, and a removable PTO cover are
provided for this purpose.
TRANSFER CASE IDENTIFICATION
An identification tag (Fig. 2) is attached to the rear
case of every NP241 transfer case. The 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. For example, • a serial number of
7-10-94 would represent July 10, 1994.
RECOMMENDED LUBRICANT AND CAPACITY
Recommended lubricant for all three transfer case
models is Mopar Dexron II, or ATF Plus. Use this
fluid for topping off the level, refilling after service,
or normal fluid changes.