Chrysler DODGE D150 1993 Service Manual page 1344

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NP205 TRANSFER CASE 21 - 343
Leakage from other sources (engine, transmission,
etc.) can be blown back onto the transfer case by air
flow under the vehicle. A blocked transfer case vent
can also cause leakage at the shaft seals due to in­
ternal pressure build up.
Overfilling the transfer case can force fluid out the
vent and be mistaken for a leak. Correct fluid level
checking methods should prevent overfill problems.
Checking Fluid Level
The correct method of checking transfer case fluid
level requires that the vehicle be level.
If fluid level is checked with the vehicle parked on
the shop floor, be sure the floor area used is level. If
a hoist is used, a drive-on, or swivel a r m type is pre­
ferred.
Allow the transfer case fluid to settle for a minute
or so before checking. Correct fluid level is to the
bottom edge of the fill plug hole.
HARD SHIFTING
Hard shifting is generally caused by:
• misadjusted or binding linkage
• loose linkage or driveline components
• torque loads caused by 4WD operation on hard
paved surfaces
• improper shifting techniques
• lack of lubricant which caused internal wear and
damage.
Loose linkage or driveline components are a result
of improperly tightened, stripped, or missing fasten­
ers. Remember t h a t loose crossmember and mounting
parts can also generate a hard shift condition.
Torque loads in the transfer case can cause hard
shifting or even prevent shifting. Such loads are gen­
erally a product of extensive operation on hard,
paved surfaces in 4WD range, unequal size tires, or
by mismatched front/rear axle gear ratios.
Linkage adjustment should be performed as de­
scribed in the service section. Improper shift and op­
erating techniques can be corrected by instructing
the driver. Internal component damage will require
overhaul to correct.
Failure to lubricate the shift linkage at recom­
mended intervals will cause the linkage to bind. If
bind is severe enough to cause hard shifting, the
linkage will have to be removed in order to correct
the condition. The linkage can be soaked in auto­
matic transmission fluid if necessary. The fluid will
break up accumulated rust and corrosion.
NOISE
Some transfer case operating noise is normal. The
rotating gear train can produce sounds t h a t may be­
come audible at higher speeds and loads. However,
unusual noise is an indicator t h a t internal compo­
nents may be worn or damaged.
Low lubricant levels are a frequent cause of noisy
operation. Insufficient lubricant will lead to over­
heating, subsequent damage to bearing and gear sur­
faces and hard shifting.
Transfer case bearing noise is higher in pitch t h a n
gear noise. If the unit is noisy in 4WD range only,
the front shaft bearings are probably at fault. If the
unit is noisy in all ranges, an overhaul will be nec­
essary to locate the faulty bearing.
Gear noise is lower in pitch and usually most no­
ticeable when engaged and under load. Gear noise in
4WD drive range only is an indicator t h a t the front
shaft gears are damaged. Noise in all ranges could be
the idler or drive gears. An overhaul will be neces­
sary to determine which is at fault.
Frequently, suspected transfer case noise may actu­
ally originate from another driveline component. The
proximity of other driveline components can some­
times make it difficult to pinpoint the noise source.
TRANSFER CASE OPERATIONAL CHECK
The transfer case should not be removed until di­
agnosis indicates the unit has actually malfunc­
tioned. If a transfer case problem is suspected, check
and verify operation before attempting repair. A
transfer case operational check may reveal t h a t a
problem is actually related to another driveline com­
ponent.
(1) Raise vehicle on a hoist t h a t will allow all four
wheels to rotate.
(2) Check lubricant level. If lubricant level is low,
check for leaks at the bearing and seal retainers,
yokes, drain/fill plugs, PTO cover and vent.
(3) If vehicle is equipped with locking hubs, en­
gage hubs.
(4) Start engine, shift transmission into gear and
operate transfer case in all ranges. Observe propeller
shaft action, shift efforts and operational sound lev­
els as follows:
(a) Only the rear propeller shaft should rotate in
two-wheel drive. Both propeller shafts should both
rotate in four-wheel drive high and low ranges.
(b) If the front propeller shaft did not rotate in
either four-wheel drive range, the transfer case
shift components may be worn or damaged. Or, if
the front shaft did rotate but the front wheels did
not, check the front axle shift mechanism and the
locking hubs (if equipped).
(c) If both propeller shafts rotate in four-wheel
drive but the wheels on one axle did not rotate, the
problem is in the axle.
(d) If neither propeller shaft rotates in any
range, the problem is in the transmission or trans­
fer case. To determine which component is at fault,
proceed to next step.
(5) Determine if fault is with transfer case or
transmission as follows: