DIAGNOSIS AND TESTING - CLUTCH AIR
PRESSURE TESTS
Inoperative clutches can be located by substituting
air pressure for fluid pressure. The clutches may be
tested by applying air pressure to their respective
passages after the valve body has been removed. Use
Special Tool 6599-1 and 6599-2 to perform test (Fig.
5).
To make air pressure tests, proceed as follows:
NOTE: The compressed air supply must be free of
all dirt and moisture. Use a pressure of 30 psi.
Remove oil pan and valve body. See Valve body
recondition.
Apply air pressure to the holes in the special tool,
one at a time.
Listen for the clutch to apply. It will give a slight
thud sound. If a large amount of air is heard escap-
ing, the transaxle must be removed from vehicle, dis-
assembled and all seals inspected.
OVERDRIVE CLUTCH
Apply air pressure to the overdrive clutch apply
passage and watch for the push/pull piston to move
forward. The piston should return to its starting
position when the air pressure is removed.
UNDERDRIVE CLUTCH
Because this clutch piston cannot be seen, its oper-
ation is checked by function. Air pressure is applied
to the low/reverse or the 2/4 clutches. This locks the
output shaft. Use a piece of rubber hose wrapped
around the input shaft and a pair of clamp-on pliers
to turn the input shaft. Next apply air pressure to
the underdrive clutch (Fig. 6). The input shaft should
not rotate with hand torque. Release the air pressure
and confirm that the input shaft will rotate.
REVERSE CLUTCH
Apply air pressure to the reverse clutch apply pas-
sage and watch for the push/pull piston to move rear-
ward. The piston should return to its starting
position when the air pressure is removed.
2/4 CLUTCH
Apply air pressure to the feed hole located on the
2/4 clutch retainer. Look in the area where the 2/4
piston contacts the first separator plate and watch
carefully for the 2/4 piston to move rearward. The
piston should return to its original position after the
air pressure is removed.
LOW/REVERSE CLUTCH
Apply air pressure to the low/reverse clutch feed
hole passage. Look in the area where the low/reverse
piston contacts the first separator plate. Watch care-
fully for the piston to move forward. The piston
should return to its original position after the air
pressure is removed.
Fig. 5 Air Pressure Test Plate
1 - AIR PRESSURE TEST PLATES
2 - 2/4 CLUTCH RETAINER HOLE
Fig. 6 Testing Underdrive Clutch
1 - AIR PRESSURE TEST PLATE 6599–1
2 - AIR NOZZLE
21 - 8 TRANSAXLE LH
42LE AUTOMATIC TRANSAXLE (Continued)
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