Heat DODGE RAM 2001 Service Repair Manual

A leak at the front of the transmission will be from
either the front bearing retainer or retainer seal.
Lubricant may be seen dripping from the clutch
housing after extended operation. If the leak is
severe, it may also contaminate the clutch disc caus-
ing the disc to slip, grab and or chatter.
A correct lubricant level check can only be made
when the vehicle is level. Also allow the lubricant to
settle for a minute or so before checking. These rec-
ommendations will ensure an accurate check and
avoid an underfill or overfill condition. Always check
the lubricant level after any addition of fluid to avoid
an incorrect lubricant level condition.
HARD SHIFTING
Hard shifting is usually caused by a low lubricant
level, improper or contaminated lubricants. The con-
sequence of using non-recommended lubricants is
noise, excessive wear, internal bind and hard shift-
ing. Substantial lubricant leaks can result in gear,
shift rail, synchro, and bearing damage. If a leak
goes undetected for an extended period, the first indi-
cations of component damage are usually hard shift-
ing and noise.
Component damage, incorrect clutch adjustment or
damaged clutch pressure plate or disc are additional
probable causes of increased shift effort. Incorrect
adjustment or a worn/damaged pressure plate or disc
can cause incorrect release. If clutch problem is
advanced, gear clash during shifts can result. Worn
or damaged synchro rings can cause gear clash when
shifting into any forward gear. In some new or
rebuilt transmissions, new synchro rings may tend to
stick slightly causing hard or noisy shifts. In most
cases this condition will decline as the rings wear-in.
TRANSMISSION NOISE
Most manual transmissions make some noise dur-
ing normal operation. Rotating gears generate a mild
whine that is audible, but generally only at extreme
speeds.
Severe highly audible transmission noise is gener-
ally the initial indicator of a lubricant problem.
Insufficient, improper or contaminated lubricant will
promote rapid wear of gears, synchros, shift rails,
forks and bearings. The overheating caused by a
lubricant problem, can also lead to gear breakage.
REMOVAL
(1) Disconnect battery negative cable.
(2) Shift transmission into Neutral.
(3) Remove shift boot screws from floorpan and
slide boot upward on the shift lever.
(4) Remove shift lever extension from shift tower
and lever assembly.(5) Remove shift tower bolts holding tower to iso-
lator plate and transmission shift cover.
(6) Remove shift tower and isolator plate from
transmission shift cover.
(7) Raise and support vehicle.
(8) Remove skid plate, if equipped.
(9) Mark propeller shaft and axle yokes for instal-
lation reference and remove shaft/shafts.
(10) Remove exhaust system Y-pipe.
(11) Disconnect speed sensor and backup light
switch connectors.
(12) Support engine with safety stand and a wood
block.
(13) If transmission is to be disassembled for,
remove drain bolt at bottom of PTO cover and drain
lubricant (Fig. 4).
TWO WHEEL DRIVE
(1) Remove nuts/bolts attaching transmission to
rear mount.
(2) Support and secure transmission with safety
chains to a transmission jack.
(3) Remove rear crossmember.
(4) Remove clutch slave cylinder bolts and move
cylinder aside for clearance.
(5) Remove transmission harness wires from clips
on transmission shift cover.
(6) Remove transmission to clutch housing bolts.
(7) Slide transmission and jack rearward until
input shaft clears clutch housing.
(8) Lower transmission jack and remove transmis-
sion from under vehicle.
FOUR WHEEL DRIVE
(1) Disconnect transfer case shift linkage at trans-
fer case range lever. Then remove transfer case shift
mechanism from transmission (Fig. 5).
(2) Support and secure transfer case to transmis-
sion jack with safety chains.
(3) Remove transfer case mounting nuts.
Fig. 4 NV4500 Drain Bolt
1 - PTO COVER
2 - DRAIN BOLT
3 - FILL PLUG
BR/BEMANUAL - NV4500 21 - 47
MANUAL - NV4500 (Continued)

(31) Remove first gear from bearing and mainshaft
(Fig. 62).
(32) Remove first gear bearing from mainshaft
(Fig. 63).
CLEANING
Clean the gears, shafts, shift components and
transmission housings with a standard parts clean-
ing solvent. Do not use acid or corrosive base sol-
vents. Dry all parts except bearings with compressed
air.
Clean the shaft bearings with a mild solvent such
as Mopartdegreasing solvent, Gunk, or similar sol-
vents. Do not dry the bearings with compressed air.
Allow the bearings to either air dry, or wipe them dry
with clean shop towels.
INSPECTION - TRANSMISSION
Inspect the reverse idler gear, bearings, shaft and
thrust washers. Replace the bearings if the rollers
are worn, chipped, cracked, flat-spotted or brinnelled.
Or if the bearing cage is damaged or distorted.
Replace the thrust washers if cracked, chipped or
worn. Replace the gear if the teeth are chipped,
cracked or worn thin.
Inspect the drive gear and bearings. Minor
scratches and burrs on the gear surfaces can be
reduced with an oil stone and 400 grit paper wetted
with oil. Replace either bearing if worn, or damaged.
Replace the gear if any teeth, splines, or bearing sur-
faces are also worn or damaged.
Inspect the front bearing retainer and bearing cup.
Replace the bearing cup if scored, cracked, brinnelled
or rough. Check the release bearing slide surface of
the retainer carefully. Minor corrosion, nicks, or pit-
ting can be smoothed with 400 grit emery and pol-
ished out with crocus cloth. Wet the abrasive paper
and crocus cloth with oil when smoothing/polishing.
Replace the retainer if worn or damaged in any way.
Do not reuse original retainer bolts. Install new bolts
during assembly.
Inspect the countershaft and bearings. Replace the
bearings if worn, rough, flat spotted or heat checked.
Check the countershaft gear teeth carefully. Small
nicks, scratches or burrs can be removed with an oil
stone and 400 grit paper wetted with oil. Replace the
shaft if any of the teeth are worn, cracked, broken or
severely chipped.
Be sure to check condition of the countershaft bear-
ing cups. Replace either bearings cup if worn, or
damaged.
Check condition of the mainshaft. Inspect all the
bearing surfaces, splines and threads. Also check con-
dition of the snap ring grooves in the hub area and
the speedometer drive gear teeth. Minor scratches or
burrs can be removed with an oil stone and polished
with crocus cloth. However, replace the shaft if any
surfaces exhibit considerable wear or damage.
Check condition of the gear case and extension or
adapter housing. Be sure the alignment dowels in the
Fig. 61 Reverse Clutch Gear
1 - REVERSE CLUTCH GEAR
Fig. 62 First Gear
1 - FIRST GEAR
Fig. 63 First Gear Bearing
1 - MAINSHAFT
2 - FIRST GEAR BEARING
21 - 64 MANUAL - NV4500BR/BE
MANUAL - NV4500 (Continued)

A leak at the front of the transmission will be from
either the front bearing retainer or retainer seal.
Lubricant may be seen dripping from the clutch
housing after extended operation. If the leak is
severe, it may also contaminate the clutch disc caus-
ing the disc to slip, grab and or chatter.
A correct lubricant level check can only be made
when the vehicle is level. Also allow the lubricant to
settle for a minute or so before checking. These rec-
ommendations will ensure an accurate check and
avoid an underfill or overfill condition. Always check
the lubricant level after any addition of fluid to avoid
an incorrect lubricant level condition.
HARD SHIFTING
Hard shifting is usually caused by a low lubricant
level, improper or contaminated lubricants. The con-
sequence of using non-recommended lubricants is
noise, excessive wear, internal bind and hard shift-
ing. Substantial lubricant leaks can result in gear,
shift rail, synchro, and bearing damage. If a leak
goes undetected for an extended period, the first indi-
cations of component damage are usually hard shift-
ing and noise.
Component damage, incorrect clutch adjustment or
damaged clutch pressure plate or disc are additional
probable causes of increased shift effort. Incorrect
adjustment or a worn/damaged pressure plate or disc
can cause incorrect release. If clutch problem is
advanced, gear clash during shifts can result. Worn
or damaged synchro rings can cause gear clash when
shifting into any forward gear. In some new or
rebuilt transmissions, new synchro rings may tend to
stick slightly causing hard or noisy shifts. In most
cases this condition will decline as the rings wear-in.
TRANSMISSION NOISE
Most manual transmissions make some noise dur-
ing normal operation. Rotating gears generate a mild
whine that is audible, but generally only at extreme
speeds.
Severe highly audible transmission noise is gener-
ally the initial indicator of a lubricant problem.
Insufficient, improper or contaminated lubricant will
promote rapid wear of gears, synchros, shift rails,
forks and bearings. The overheating caused by a
lubricant problem, can also lead to gear breakage.
REMOVAL
NOTE: Use a heavy duty scissors style transmis-
sion jack for remove of the transmission.
(1) Disconnect battery negative cable.
(2) Shift transmission into Neutral.
(3) Remove screws attaching shift boot to floorpan.
Then slide boot upward on the shift lever.(4) Remove the bolts holding the shift tower to the
isolator plate and transmission gear case.
(5) Remove the shift tower and isolator plate from
the transmission gear case.
(6) Raise and support vehicle.
(7) Remove skid plate, if equipped.
(8) Mark propeller shaft/shafts and axle yokes for
installation reference.
(9) Remove propeller shaft.
(10) Disconnect and remove exhaust system as
necessary.
(11) Disconnect wires at backup light switch.
(12) Support engine with adjustable safety stand
and wood block.
(13) If transmission is to be disassembled for
repair, remove drain bolt at bottom of PTO cover and
drain lubricant from transmission (Fig. 4).
(14) Remove clutch slave cylinder splash shield, if
equipped.
(15) Remove clutch slave cylinder bolts and move
cylinder aside for clearance.
(16) Remove wire harness from clips on transmis-
sion.
TWO WHEEL DRIVE
(1) Remove bolts/nuts mounting transmission to
the rear mount.
(2) Support and secure transmission with safety
chains to a transmission jack.
(3) Remove rear crossmember.
(4) Remove transmission clutch housing bolts at
the engine block.
(5) Slide transmission and jack rearward until
input shaft clears clutch disc and pressure plate.
(6) Lower transmission jack and remove transmis-
sion from under vehicle.
Fig. 4 NV5600 Drain Bolt
1 - PTO COVER
2 - DRAIN BOLT
21 - 94 MANUAL - NV5600BR/BE
MANUAL - NV5600 (Continued)

(7) Remove output shaft nut with Wrench 8226 on
the shaft nut and Socket 6993 or 6984 to hold the
shaft (Fig. 22). Discard output shaft nut from the
output shaft.
NOTE: If necessary strike the flat side area of
Wrench 8226 with a hammer to break the nut loose.
(8) Remove output shaft ball bearing assembly and
reverse thrust washer from the output shaft (Fig.
23).(9) Remove reverse gear, reverse gear synchronizer
cone, reverse gear outer blocker ring and reverse
gear bearing (Fig. 24).
(10) Remove reverse gear bearing sleeve from the
output shaft (Fig. 25).
NOTE: If necessary heat the sleeve slightly with a
heat gun. Do not use a torch to heat the sleeve or
damage to the output shaft may occur.
(11) Remove roll-pin securing the reverse shift fork
to the reverse shift rail. Use a 6mm (7/32 inch)
punch and hammer.
(12) Remove reverse shift fork and synchronizer as
an assembly from the reverse shift rail and the out-
put shaft (Fig. 26).
Fig. 22 Output Shaft Nut
1 - WRENCH 8226
2 - SOCKET 6993
Fig. 23 INSTALL OUTPUT SHAFT BEARING
1 - OUTPUT SHAFT BALL BEARING
2 - THRUST WASHER
Fig. 24 REVERSE GEAR COMPONENTS
1 - REVERSE GEAR
2 - REVERSE BEARING
3 - BLOCKER RING
4 - FRICTION CONE
21 - 100 MANUAL - NV5600BR/BE
MANUAL - NV5600 (Continued)

and crocus cloth with oil when smoothing/polishing.
Replace the retainer if worn or damaged in any way.
Do not reuse original retainer bolts. Install new bolts
during assembly.
Inspect the countershaft and bearings. Replace the
bearings if worn, rough, flat spotted or heat checked.
Check the countershaft gear teeth carefully. Small
nicks, scratches or burrs can be removed with an oil
stone and 400 grit paper wetted with oil. Replace the
shaft if any of the teeth are worn, cracked, broken or
severely chipped.
Be sure to check condition of the countershaft bear-
ing cups. Replace either bearings cup if worn, or
damaged.
Check condition of the mainshaft. Inspect all the
bearing surfaces, splines and threads. Also check con-
dition of the snap ring grooves in the hub area and
the speedometer drive gear teeth. Minor scratches or
burrs can be removed with an oil stone and polished
with crocus cloth. However, replace the shaft if any
surfaces exhibit considerable wear or damage.
Check condition of the gear case and extension or
adapter housing. Be sure the alignment dowels in the
case top surface and in the housing/adapter are tight
and in good condition.
Run a tap through the gear case bolt holes if the
threads need minor cleanup. Helicoil inserts can be
used to repair seriously damaged threaded holes if
necessary.
Be sure all case and housing/adapter sealing and
mating surfaces are free of burrs and nicks. This is
especially important as gaskets are not used in the
transmission. Minor nicks and scratches on the seal-
ing surfaces can be dressed off with a fine tooth file
or oil stone.
Replace the gear case or housing/adapter if cracked
or broken. Do not attempt to repair this type of dam-
age by welding or brazing.
Check condition of the countershaft fifth gear com-
ponents. This includes the shift lug and rail located
in the gear case and the rail bushings.
Inspect the gear and hub assembly. Minor burrs
can be cleaned up with an oil stone. However, the
gear and hub assembly should be replaced if the
teeth or splines are excessively worn, or damaged.
The synchro sleeve should also be replaced if worn or
damaged in any way. Do not reuse synchro struts
that are worn or springs that are collapsed or
severely distorted. Replace worn distorted synchro
parts to avoid shift problems after assembly and
installation.
The shift fork should be inspected for evidence of
wear and distortion. Check fit of the sleeve in the
fork to be sure the two parts fit and work smoothly.
Replace the fork if the roll pin holes are worn over-
size or damaged. Do not attempt to salvage a wornfork. It will cause shift problems later on. Replace
shift fork roll pins if necessary or if doubt exists
about their condition.
The bearings should be examined carefully for
wear, roughness, flat spots, pitting or other damage.
Replace the bearings if necessary.
Inspect the blocker ring and clutch gear. replace
either part if worn or damaged in any way. Also be
sure replacement parts fit properly before proceeding
with assembly.
Examine the 1-2 synchro hub and sleeve for wear
or damage. Replace sleeve and hub if the splines are
worn, chipped or damaged.
Replace the synchro struts if worn, or chipped. Also
replace the springs if collapsed, distorted or broken.
Inspect the mainshaft geartrain components.
Check teeth on all gears, hubs, clutch gears, stop
rings and clutch rings. The teeth must be in good
condition and not worn, cracked or chipped. Replace
any component that exhibits wear or damage.
Examine the synchro stop rings, clutch rings and
clutch gears. Replace any part that exhibits wear,
distortion or damage. Replace the clutch rings if the
friction material is burned, flaking off or worn.
Inspect all of the thrust washers and locating pins.
Replace the pins if bent or worn. Replace the wash-
ers if worn or the locating pin notches are distorted.
Check condition of the synchro struts and springs.
Replace these parts if worn, cracked or distorted.
ASSEMBLY
NOTE: Gaskets are not used in the transmission.
Use MoparTGasket Maker or equivalent on all gear
case and extension housing sealing surfaces.
OUTPUT SHAFT
(1) Place second gear on bench with the synchro
clutch ring up.
(2) Install second gear synchro inner blocker ring
onto second gear (Fig. 53).
(3) Install second gear synchro friction cone over
the blocker ring and onto second gear (Fig. 54).
(4) Install second gear synchro outer blocker ring
over the second gear synchro friction cone. Align one
of the lugs on the outer ring with a lug on the inner
ring (Fig. 55).
(5) Install 1-2 synchro assembly onto the second
gear assembly (Fig. 56).
(6) Reverse assembly on the bench.
21 - 110 MANUAL - NV5600BR/BE
MANUAL - NV5600 (Continued)

FLUID AND FILTER
DIAGNOSIS AND TESTING - EFFECTS OF
INCORRECT FLUID LEVEL
A low fluid level allows the pump to take in air
along with the fluid. Air in the fluid will cause fluid
pressures to be low and develop slower than normal.
If the transmission is overfilled, the gears churn the
fluid into foam. This aerates the fluid and causing
the same conditions occurring with a low level. In
either case, air bubbles cause fluid overheating, oxi-
dation and varnish buildup which interferes with
valve and clutch operation. Foaming also causes fluid
expansion which can result in fluid overflow from the
transmission vent or fill tube. Fluid overflow can eas-
ily be mistaken for a leak if inspection is not careful.
DIAGNOSIS AND TESTING - CAUSES OF
BURNT FLUID
Burnt, discolored fluid is a result of overheating
which has two primary causes.
(1) A result of restricted fluid flow through the
main and/or auxiliary cooler. This condition is usu-
ally the result of a faulty or improperly installed
drainback valve, a damaged main cooler, or severe
restrictions in the coolers and lines caused by debris
or kinked lines.
(2) Heavy duty operation with a vehicle not prop-
erly equipped for this type of operation. Trailer tow-
ing or similar high load operation will overheat the
transmission fluid if the vehicle is improperly
equipped. Such vehicles should have an auxiliary
transmission fluid cooler, a heavy duty cooling sys-
tem, and the engine/axle ratio combination needed to
handle heavy loads.
DIAGNOSIS AND TESTING - FLUID
CONTAMINATION
Transmission fluid contamination is generally a
result of:
²adding incorrect fluid
²failure to clean dipstick and fill tube when
checking level
²engine coolant entering the fluid
²internal failure that generates debris
²
overheat that generates sludge (fluid breakdown)
²failure to reverse flush cooler and lines after repair
²failure to replace contaminated converter after
repair
The use of non-recommended fluids can result in
transmission failure. The usual results are erratic
shifts, slippage, abnormal wear and eventual failure
due to fluid breakdown and sludge formation. Avoid
this condition by using recommended fluids only.
The dipstick cap and fill tube should be wiped clean
before checking fluid level. Dirt, grease and other for-
eign material on the cap and tube could fall into the
tube if not removed beforehand. Take the time to wipe
the cap and tube clean before withdrawing the dipstick.
Engine coolant in the transmission fluid is gener-
ally caused by a cooler malfunction. The only remedy
is to replace the radiator as the cooler in the radiator
is not a serviceable part. If coolant has circulated
through the transmission, an overhaul is necessary.
The transmission cooler and lines should be
reverse flushed whenever a malfunction generates
sludge and/or debris. The torque converter should
also be replaced at the same time.
Failure to flush the cooler and lines will result in
recontamination. Flushing applies to auxiliary coolers
as well. The torque converter should also be replaced
whenever a failure generates sludge and debris. This is
necessary because normal converter flushing procedures
will not remove all contaminants.
STANDARD PROCEDURE - FLUID LEVEL
CHECK
Low fluid level can cause a variety of conditions
because it allows the pump to take in air along with
the fluid. As in any hydraulic system, air bubbles
make the fluid spongy, therefore, pressures will be
low and build up slowly.
Improper filling can also raise the fluid level too
high. When the transmssion has too much fluid, the
geartrain churns up foam and cause the same condi-
tions which occur with a low fluid level.
In either case, air bubbles can cause overheating
and/or fluid oxidation, and varnishing. This can inter-
fere with normal valve, clutch, and accumulator opera-
tion. Foaming can also result in fluid escaping from the
transmission vent where it may be mistaken for a leak.
Along with fluid level, it is important to check the
condition of the fluid. When the fluid smells burned,
and is contaminated with metal or friction material
particles, a complete transmission recondition is
needed. Be sure to examine the fluid on the dipstick
closely. If there is any doubt about its condition,
drain out a sample for a double check.
After the fluid has been checked, seat the dipstick
fully to seal out water and dirt.
The transmission has a dipstick to check oil level.
It is located on the right side of the engine. Be sure
to wipe all dirt from dipstick handle before removing.
Fluid level is checked with the engine running at curb
idle speed, the transmission in NEUTRAL and the trans-
mission fluid at normal operating temperature.The
engine should be running at idle speed for at least
one minute, with the vehicle on level ground.
The transmission fluid level can be checked two
ways.
BR/BEAUTOMATIC TRANSMISSION - 42RE 21 - 199

ADJUSTMENT PROCEDURE
(1) Turn ignition switch to OFF position.
(2) Remove air cleaner if necessary.
(3) Disconnect cable end from attachment stud.
Carefully slide cable off stud. Do not pry or pull
cable off.
(4) Verify that transmission throttle lever is in
fully closed position. Then be sure lever on throttle
body is at curb idle position.
(5) Pry the T.V. cable lock (A) into the UP position
(Fig. 233). This will unlock the cable and allow for
readjustment.
(6) Apply just enough tension on the T.V. cable (B)
to remove any slack in the cable.Pulling too tight
will cause the T.V. lever on the transmission to
move out of its idle position, which will result
in an incorrect T.V. cable adjustment.Slide the
sheath of the T.V. cable (D) back and forth until the
centerlines of the T.V. cable end (B) and the throttle
bell crank lever (C) are aligned within one millimeter
(1mm) (Fig. 233).
(7) While holding the T.V. cable in the set position
push the T.V. cable lock (A) into the down position
(Fig. 233). This will lock the present T.V. cable
adjustment.NOTE: Be sure that as the cable is pulled forward
and centered on the throttle lever stud, the cable
housing moves smoothly with the cable. Due to the
angle at which the cable housing enters the spring
housing, the cable housing may bind slightly and
create an incorrect adjustment.
(8) Reconnect the T.V. cable (B) to the throttle
bellcrank lever (C).
(9) Check cable adjustment. Verify transmission
throttle lever and lever on throttle body move simul-
taneously.
Fig. 232 Throttle Valve Cable at Transmission
1 - TRANSMISSION SHIFTER CABLE
2 - THROTTLE VALVE CABLE
3 - TRANSFER CASE SHIFTER CABLE
4 - TRANSFER CASE SHIFTER CABLE BRACKET RETAINING
BOLT(1OR2)
5 - THROTTLE VALVE CABLE BRACKET RETAINING BOLT
6 - ELECTRICAL CONNECTORS
7 - TRANSMISSION FLUID LINES
Fig. 233 Throttle Valve Cable at Throttle Linkage
1 - THROTTLE LINKAGE
2 - THROTTLE VALVE CABLE LOCKING CLIP
3 - THROTTLE VALVE CABLE
BR/BEAUTOMATIC TRANSMISSION - 42RE 21 - 255
THROTTLE VALVE CABLE (Continued)

TORQUE CONVERTER
DRAINBACK VALVE
DESCRIPTION
The drainback valve is located in the transmission
cooler outlet (pressure) line.
OPERATION
The valve prevents fluid from draining from the
converter into the cooler and lines when the vehicle
is shut down for lengthy periods. Production valves
have a hose nipple at one end, while the opposite end
is threaded for a flare fitting. All valves have an
arrow (or similar mark) to indicate direction of flow
through the valve.
STANDARD PROCEDURE - TORQUE
CONVERTER DRAINBACK VALVE
The converter drainback check valve is located in
the cooler outlet (pressure) line near the radiator
tank. The valve prevents fluid drainback when the
vehicle is parked for lengthy periods. The valve check
ball is spring loaded and has an opening pressure of
approximately 2 psi.
The valve is serviced as an assembly; it is not
repairable. Do not clean the valve if restricted, or
contaminated by sludge, or debris. If the valve fails,
or if a transmission malfunction occurs that gener-
ates significant amounts of sludge and/or clutch par-
ticles and metal shavings, the valve must be
replaced.
The valve must be removed whenever the cooler
and lines are reverse flushed. The valve can be flow
tested when necessary. The procedure is exactly the
same as for flow testing a cooler.
If the valve is restricted, installed backwards, or in
the wrong line, it will cause an overheating condition
and possible transmission failure.
CAUTION: The drainback valve is a one-way flow
device. It must be properly oriented in terms of flow
direction for the cooler to function properly. The
valve must be installed in the pressure line. Other-
wise flow will be blocked and would cause an over-
heating condition and eventual transmission failure.
TRANSMISSION
TEMPERATURE SENSOR
DESCRIPTION
Transmission fluid temperature readings are sup-
plied to the transmission control module by the ther-
mistor (Fig. 243). The temperature readings are used
to control engagement of the fourth gear overdrive
clutch, the converter clutch, and governor pressure.
Normal resistance value for the thermistor at room
temperature is approximately 1000 ohms.
The thermistor is part of the governor pressure
sensor assembly and is immersed in transmission
fluid at all times.
OPERATION
The PCM prevents engagement of the converter
clutch and overdrive clutch, when fluid temperature
is below approximately 10ÉC (50ÉF).
If fluid temperature exceeds 126ÉC (260ÉF), the
PCM causes a 4-3 downshift and engage the con-
verter clutch. Engagement is according to the third
gear converter clutch engagement schedule.
The overdrive OFF lamp in the instrument panel
illuminates when the shift back to third occurs. The
transmission will not allow fourth gear operation
until fluid temperature decreases to approximately
110ÉC (230ÉF).
Fig. 243 Governor Pressure Sensor
1 - GOVERNOR BODY
2 - GOVERNOR PRESSURE SENSOR/TRANSMISSION FLUID
TEMPERATURE THERMISTOR
21 - 262 AUTOMATIC TRANSMISSION - 42REBR/BE

REGULATOR VALVE
The pressure regulator valve is needed to control
the hydraulic pressure within the system and reduce
the amount of heat produced in the fluid. The pres-
sure regulator valve is located in the valve body near
the manual valve. The pressure regulator valve train
controls the maximum pressure in the lines by
metering the dumping of fluid back into the sump.
Regulated pressure is referred to as ªline pressure.º
The regulator valve (Fig. 248) has a spring on one
end that pushes the valve to the left. This closes a
dump (vent) that is used to lower pressure. The clos-
ing of the dump will cause the oil pressure to
increase. Oil pressure on the opposite end of the
valve pushes the valve to the right, opening the
dump and lowering oil pressure. The result is spring
pressure working against oil pressure to maintain
the oil at specific pressures. With the engine run-
ning, fluid flows from the pump to the pressure reg-
ulator valve, manual valve, and the interconnected
circuits. As fluid is sent through passages to the reg-
ulator valve, the pressure pushes the valve to the
right against the large spring. It is also sent to the
reaction areas on the left side of the throttle pressure
plug and the line pressure plug. With the gear selec-
tor in the PARK position, fluid recirculates through
the regulator and manual valves back to the sump.Meanwhile, the torque converter is filled slowly. In
all other gear positions (Fig. 249), fluid flows
between two right side lands to the switch valve and
torque converter. At low pump speeds, the flow is
controlled by the pressure valve groove to reduce
pressure to the torque converter. After the torque
converter and switch valve fill with fluid, the switch
valve becomes the controlling metering device for
torque converter pressure. The regulator valve then
begins to control the line pressure for the other
transmission circuits. The balance of the fluid pres-
sure pushing the valve to the right and the spring
pressure pushing to the left determines the size of
the metering passage at land #2 (land #1 being at
the far right of the valve in the diagram). As fluid
leaks past the land, it moves into a groove connected
to the filter or sump. As the land meters the fluid to
the sump, it causes the pressure to reduce and the
spring decreases the size of the metering passage.
When the size of the metering passage is reduced,
the pressure rises again and the size of the land is
increased again. Pressure is regulated by this con-
stant balance of hydraulic and spring pressure.
The metering at land #2 establishes the line pres-
sure throughout the transmission. It is varied accord-
ing to changes in throttle position and the
transmission's internal condition within a range of
Fig. 248 Regulator Valve in PARK Position
21 - 268 AUTOMATIC TRANSMISSION - 42REBR/BE
VALVE BODY (Continued)

FLUID AND FILTER
DIAGNOSIS AND TESTING - EFFECTS OF
INCORRECT FLUID LEVEL
A low fluid level allows the pump to take in air
along with the fluid. Air in the fluid will cause fluid
pressures to be low and develop slower than normal.
If the transmission is overfilled, the gears churn the
fluid into foam. This aerates the fluid and causing
the same conditions occurring with a low level. In
either case, air bubbles cause fluid overheating, oxi-
dation and varnish buildup which interferes with
valve and clutch operation. Foaming also causes fluid
expansion which can result in fluid overflow from the
transmission vent or fill tube. Fluid overflow can eas-
ily be mistaken for a leak if inspection is not careful.
DIAGNOSIS AND TESTING - CAUSES OF
BURNT FLUID
Burnt, discolored fluid is a result of overheating
which has two primary causes.
(1)
A result of restricted fluid flow through the main
and/or auxiliary cooler. This condition is usually the
result of a faulty or improperly installed drainback
valve, a damaged main cooler, or severe restrictions in
the coolers and lines caused by debris or kinked lines.
(2) Heavy duty operation with a vehicle not prop-
erly equipped for this type of operation. Trailer tow-
ing or similar high load operation will overheat the
transmission fluid if the vehicle is improperly
equipped. Such vehicles should have an auxiliary
transmission fluid cooler, a heavy duty cooling sys-
tem, and the engine/axle ratio combination needed to
handle heavy loads.
DIAGNOSIS AND TESTING - FLUID
CONTAMINATION
Transmission fluid contamination is generally a
result of:
²adding incorrect fluid
²failure to clean dipstick and fill tube when
checking level
²engine coolant entering the fluid
²internal failure that generates debris
²
overheat that generates sludge (fluid breakdown)
²failure to reverse flush cooler and lines after repair
²failure to replace contaminated converter after
repair
The use of non-recommended fluids can result in
transmission failure. The usual results are erratic
shifts, slippage, abnormal wear and eventual failure
due to fluid breakdown and sludge formation. Avoid
this condition by using recommended fluids only.
The dipstick cap and fill tube should be wiped
clean before checking fluid level. Dirt, grease andother foreign material on the cap and tube could fall
into the tube if not removed beforehand. Take the
time to wipe the cap and tube clean before withdraw-
ing the dipstick.
Engine coolant in the transmission fluid is gener-
ally caused by a cooler malfunction. The only remedy
is to replace the radiator as the cooler in the radiator
is not a serviceable part. If coolant has circulated
through the transmission, an overhaul is necessary.
The transmission cooler and lines should be
reverse flushed whenever a malfunction generates
sludge and/or debris. The torque converter should
also be replaced at the same time.
Failure to flush the cooler and lines will result in
recontamination. Flushing applies to auxiliary coolers
as well. The torque converter should also be replaced
whenever a failure generates sludge and debris. This is
necessary because normal converter flushing procedures
will not remove all contaminants.
STANDARD PROCEDURE - FLUID LEVEL
CHECK
Low fluid level can cause a variety of conditions
because it allows the pump to take in air along with
the fluid. As in any hydraulic system, air bubbles
make the fluid spongy, therefore, pressures will be
low and build up slowly.
Improper filling can also raise the fluid level too
high. When the transmssion has too much fluid, the
geartrain churns up foam and cause the same condi-
tions which occur with a low fluid level.
In either case, air bubbles can cause overheating
and/or fluid oxidation, and varnishing. This can
interfere with normal valve, clutch, and accumulator
operation. Foaming can also result in fluid escaping
from the transmission vent where it may be mis-
taken for a leak.
Along with fluid level, it is important to check the
condition of the fluid. When the fluid smells burned,
and is contaminated with metal or friction material
particles, a complete transmission recondition is
needed. Be sure to examine the fluid on the dipstick
closely. If there is any doubt about its condition,
drain out a sample for a double check.
After the fluid has been checked, seat the dipstick
fully to seal out water and dirt.
The transmission has a dipstick to check oil level.
It is located on the right side of the engine. Be sure
to wipe all dirt from dipstick handle before removing.
Fluid level is checked with the engine running at
curb idle speed, the transmission in NEUTRAL and the
transmission fluid at normal operating temperature.
The engine should be running at idle speed for at
least one minute, with the vehicle on level
ground.
The transmission fluid level can be checked two ways.
21 - 370 AUTOMATIC TRANSMISSION - 44REBR/BE