Dodge RAM TRUCK 1500 1995 Service Manual page 1391

21 - 108 42RH/46RH/47RH TRANSMISSION DIAGNOSIS AND TESTING
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 radia­
tor, is not a serviceable part. If coolant has circulated
through the transmission for some time, an overhaul
may also be necessary; especially if shift problems
had developed.
The transmission cooler and lines should be reverse
flushed whenever a malfunction generates sludge
and/or debris. The converter and drainback valve
should also be replaced.
Failure to flush the cooler and lines will result in
re-contamination and a shop comeback. Flushing ap­
plies to auxiliary coolers as well. The torque con­
verter and drainback valve should also be replaced
whenever a failure generates sludge and debris. This
is necessary because converter flushing procedures
will not remove all of the contaminants.
OVERDRIVE FOURTH GEAR ELECTRICAL
CONTROLS
The electrical controls governing the shift into
fourth gear consist of the control switch on the in­
strument panel and the overdrive solenoid on the
valve body. The control switch is in circuit with the
solenoid and must be in the On position to energize
the solenoid. The transmission must also have
reached third gear range before the shift to fourth
gear will occur.
The selector switch, valve body solenoid, case con­
nectors and related wiring can all be tested with a 12
volt test lamp or a volt/ohmmeter. Check continuity
of each component when diagnosis indicates this is
necessary.
Switch and solenoid continuity should be checked
whenever the transmission fails to shift into fourth
gear range.
If the fluid temperature indicator lamp comes on,
fluid temperature is either at, or above 285°F. This
indicates an approaching. overheat condition. The
sensor will downshift the transmission to third gear
and possibly disengage the converter clutch. At this
point, it will be necessary to determine the cause of
the overheat condition (e.g. cooler restricted, blocked,
vehicle overloaded, not equipped for towing, etc.).
THROTTLE VALVE CABLE ADJUSTMENT
Throttle valve cable adjustment is important to
proper operation. This adjustment positions the
throttle valve which controls shift speed, quality and
part throttle downshift sensitivity.
If cable setting is too short, early shifts and slip­
page between shifts may occur. If the setting is too
long, shifts may be delayed and part throttle down­
shifts may be very sensitive. Refer to the In-Vehicle
Service section for adjustment procedure.
GEARSHIFT LINKAGE
Gearshift linkage adjustment is important because
it positions the valve body manual valve. Incorrect
adjustment will cause creeping in Neutral, prema­
ture clutch wear, delayed engagement in any gear, or
a no-start in Park or Neutral position.
Proper operation of the park/neutral position
switch will provide a quick check of linkage adjust­
ment. Refer to the In-Vehicle Service section for ad­
justment procedure.
ROAD TESTING
Before road testing, be sure the fluid level and all
linkage adjustments have been checked and adjusted
if necessary. Observe engine performance during the
road test. A poorly tuned engine will not allow an ac­
curate analysis of transmission operation.
Operate the transmission in all gear ranges. Check
for shift variations and engine flare, which indicates
slippage. Note if shifts are harsh, spongy, delayed,
early, or if part throttle downshifts are sensitive.
Slippage indicated by engine flare, usually means
clutch, band or overrunning clutch problems. If the
condition is advanced, an overhaul may be necessary
to restore normal operation.
A slipping clutch or band can often be determined
by comparing which internal units are applied in the
various gear ranges. The Clutch and Band Applica­
tion charts (Fig. 1) provide a basis for analyzing road
test results.
ANALYZING THE ROAD TEST
Refer to the Clutch and Band Application charts
(Fig. 2) and note which elements are in use in the
various gear ranges.
Note that the rear clutch is applied in all forward
ranges (D, 2, 1). The transmission overrunning clutch
is applied in first gear (D, 2 and 1 ranges) only. The
rear band is applied in 1 and R range only.
Note that the overdrive clutch is applied only in
fourth gear and the overdrive direct clutch and over­
running clutch are applied in all ranges except fourth
gear.
For example: If slippage occurs in first gear in D
and 2 range but not in 1 range, the transmission
overrunning clutch is faulty. Similarly, if slippage oc­
curs in any two forward gears, the rear clutch is slip­
ping.
Applying the same method of analysis, note that
the front and rear clutches are applied simulta­
neously only in D range third and fourth gear. If the
transmission slips in third gear, either the front
clutch or the rear clutch is slipping.