Automatic Transmissions and Transaxles, A2, 3rd Edition Page 408 (408 of 685)

plates, a sign of prolonged slippage. See Figure 17-17.
Also, check the tangs for wear or damage. Figure 17-18
shows a used steel plate. This plate is shiny, which is
normal for a used plate, and could be reused if necessary.
If there is any doubt about the condition of the plates, they
should be replaced. Steel plates are sometimes included in
a transmission overhaul kit.
Friction discs are normally replaced as part of a trans-
mission overhaul and are usually included in a transmis-
sion overhaul kit. Worn or damaged discs may be charred,
glazed, or heavily pitted. The friction lining may scrape off
easily with your fingernail. See Figure 17-19. In some
instances, all the friction material will be missing from the
friction discs. Figure 17-20 shows a friction disc that has
lost almost all its friction material.
Check the condition of the channels on the inside
surface of the clutch drum and the splines on the clutch
hub. Severe disc damage may cause the hub splines to be
stripped. Worn or damaged parts should be replaced.
Removing the Apply Piston
Rebuilding a clutch pack requires the use of a special
spring compressor, Figure 17-21. Install the spring
compressor and compress the return spring. Remove the
retaining snap ring with snap ring pliers or a screwdriver.
Release the spring compressor; then remove the spring
retainer and the return spring or springs.
Remove the clutch apply piston from the drum,
Figure 17-22. If the piston sticks in the drum, it can
sometimes be removed by slamming the drum downward
on a block of wood or a wooden workbench. This will
408 Automatic Transmissions and Transaxles
Figure 17-17. This plate was scored by the scraping action of
foreign material between the plate and the friction disc.The foreign
material may be from another part of the transmission or transaxle,
or it may be the result of severe damage to the friction discs.
Figure 17-18. A normally worn steel plate will be shiny as
shown here. This steel plate could be reused if necessary.
Before deciding that the plate is good, however, check it for
warping and damage to the teeth.
Figure 17-19. If friction disc material can be scraped off with a
fingernail, the friction material is burned. A disc in this condition
cannot be reused and should be discarded.
Figure 17-20. The friction material of a friction disc will some-
times wear away completely, leaving the steel backing exposed.
This disc should be replaced.Water in the transmission will also
cause the friction material to separate from the steel backing.

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Extracted Text (may have errors)

plates, a sign of prolonged slippage. See Figure 17-17.
Also, check the tangs for wear or damage. Figure 17-18
shows a used steel plate. This plate is shiny, which is
normal for a used plate, and could be reused if necessary.
If there is any doubt about the condition of the plates, they
should be replaced. Steel plates are sometimes included in
a transmission overhaul kit.
Friction discs are normally replaced as part of a trans-
mission overhaul and are usually included in a transmis-
sion overhaul kit. Worn or damaged discs may be charred,
glazed, or heavily pitted. The friction lining may scrape off
easily with your fingernail. See Figure 17-19. In some
instances, all the friction material will be missing from the
friction discs. Figure 17-20 shows a friction disc that has
lost almost all its friction material.
Check the condition of the channels on the inside
surface of the clutch drum and the splines on the clutch
hub. Severe disc damage may cause the hub splines to be
stripped. Worn or damaged parts should be replaced.
Removing the Apply Piston
Rebuilding a clutch pack requires the use of a special
spring compressor, Figure 17-21. Install the spring
compressor and compress the return spring. Remove the
retaining snap ring with snap ring pliers or a screwdriver.
Release the spring compressor; then remove the spring
retainer and the return spring or springs.
Remove the clutch apply piston from the drum,
Figure 17-22. If the piston sticks in the drum, it can
sometimes be removed by slamming the drum downward
on a block of wood or a wooden workbench. This will
408 Automatic Transmissions and Transaxles
Figure 17-17. This plate was scored by the scraping action of
foreign material between the plate and the friction disc.The foreign
material may be from another part of the transmission or transaxle,
or it may be the result of severe damage to the friction discs.
Figure 17-18. A normally worn steel plate will be shiny as
shown here. This steel plate could be reused if necessary.
Before deciding that the plate is good, however, check it for
warping and damage to the teeth.
Figure 17-19. If friction disc material can be scraped off with a
fingernail, the friction material is burned. A disc in this condition
cannot be reused and should be discarded.
Figure 17-20. The friction material of a friction disc will some-
times wear away completely, leaving the steel backing exposed.
This disc should be replaced.Water in the transmission will also
cause the friction material to separate from the steel backing.

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often jar the piston loose. Compressed air can also be used
to blow the piston from the drum. Place the drum down-
ward on the workbench and insert an air nozzle in the oil
feed hole in the center of the drum. A short burst of air
should push out the piston.
With the piston out of the drum, remove the piston
seals. Hard or cracked seals indicate that the clutch has been
overheated. If there is also a seal around the interior (hub) of
the clutch drum (inner piston seal), remove it, Figure 17-23.
Then, thoroughly clean the piston and piston bore.
Often, clutch apply pistons and clutch assemblies are
installed in the rear of the case. Disassembly and assembly
procedures for these assemblies are similar to those for
other clutch packs.
Inspect the piston for cracks. Also check that the air
bleed check ball is free.
Obtain new piston seals. Compare the new seals to the
old ones to ensure that you are installing the proper seals
on the piston. In addition, check the fit of the new seals by
placing them in the piston bore. They should fit snugly. A
bulge, or buckle, in an outer piston seal means the seal’s
diameter is too large. A gap between an outer piston seal
and the piston bore means the diameter is too small.
Before installing the new piston seals, lubricate them
with transmission fluid. Petroleum jelly can also be used,
but other types of oil or grease will damage the seals.
Carefully install the new piston seals on the clutch drum
hub and clutch piston, as applicable. The new seals should
fit snugly, but not too snugly. Lip seals must be installed on
a piston so the sealing lip will be directed toward the
hydraulic pressure (toward the back of the drum).
Install the clutch piston in its bore. The type of piston
seal determines the installation method. If O-ring seals are
Chapter 17 Rebuilding Automatic Transmissions and Transaxles 409
Return
springs
Compressor
tool
Remove
piston
snap ring
Figure 17-21. A special compressor must be used to remove
the clutch apply piston in order to get at the seals of the clutch
assembly. Universal tools are available that fit all types of
assemblies. (DaimlerChrysler)
Snap ring
Spring
retainer
Piston
O-ring
Return spring
Drum
assembly
Figure 17-22. Exploded view of a clutch apply piston and
related parts shows parts that must be removed during
rebuilding. (Nissan)
Warning: When using compressed air to
remove a piston, point the open end of the
drum away from yourself and others. Direct
the piston into a pile of rags or another soft surface
so that it does not fly out and become damaged or
cause injury. Also, use a regulated amount of air
pressure.
Note: If the check ball is missing, do not
attempt to install a replacement check ball.
Replace the apply piston.
Figure 17-23. Inner piston seals can usually be removed
with a small pick. Inspect the seals carefully for damage and
excessive wear.

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mine the amount of endplay, Figure 17-13. Planetary
gearsets often contain bushings or needle bearings that
wear out. These should be carefully checked, as well. Any
parts that are worn or damaged should be replaced.
Visually inspect needle bearings and Torrington (flat)
bearings and try to rotate them by hand. If you feel any
roughness when turning a clean bearing or a gear that rides
on a bearing, replace the bearing. If you suspect that a
bearing inside a gearset is worn, take the time to disas-
semble the gearset and check the bearing.
Bushings can be checked visually. If a bushing shows signs
of wear or scoring, replace it. A bushing that looks good can
be excessively worn. Check bushings for wear by inserting
the mating shaft or race into the bushing and trying to rock
the shaft or race back and forth. If the shaft or race rocks
excessively, the bushing is loose and should be replaced.
Clutch Pack Service
One of the most important parts of automatic trans-
mission overhaul is the proper checking and rebuilding of
the clutch packs. These operations are discussed in the
following sections.
Clutch Pack Disassembly and Inspection
To begin disassembly, use a screwdriver to remove the
snap ring that holds the plates and friction discs in the
clutch drum. See Figure 17-14. Then, remove the plates
and discs. Unless they are excessively worn, the discs and
plates will fall out when the drum is turned over. Keep all
the steel plates together, noting if there are any reaction
plates (thicker steel plates) at the top and bottom of the
stack, Figure 17-15. Never interchange one set of clutch
pack parts with another.
Inspect the steel plates. Look for discoloration, which
is caused by overheating and is often a sign of a badly
slipping clutch pack. A common sign of overheating is
leopard spotting, Figure 17-16. Look for worn or scored
Chapter 17 Rebuilding Automatic Transmissions and Transaxles 407
Carrier
Feeler
gauge
Planet
gear
Clearance
Figure 17-13. The planet gears and planet carrier can be
checked for wear with a feeler gauge, as shown here.
Disassembly is not required to make this check. (Nissan)
Fourth clutch
snap ring
Tool
Remove
discs
and plates
Figure 17-14. The clutch packs should be disassembled to
check for burned friction discs and other problems. Most clutch
packs are held together with a large snap ring, as shown here.
(General Motors)
Direct
clutch pack
Keep parts
together and
in sequence
Sliding hub
Figure 17-15. Inspect the clutch plates for wear, burning,
scoring, and other damage. Also, check the drum, bushings,
hub splines, and thrust washers. Replace parts that show signs
of wear or damage. (DaimlerChrysler)
Figure 17-16. Steel plates showing leopard spots are often
found when the transmission or transaxle is disassembled.
Leopard spots are named for their resemblance to a leopard’s
coat and are a sign of severe clutch overheating. The dark
spots are areas where the metal has become so overheated
that it has lost its strength and resistance to wear.

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