Copyright by Goodheart-Willcox Co., Inc.
Chapter 15 Transmission and Transaxle In-Vehicle Service 375
Inspect
inside pan
Filter
Valve
body
Case
Figure 15-17. Remove the oil pan and check for metal
particles, varnish buildup, and sludge. Note that some oil pans
have a small magnet to pick up metal pieces. Be careful not to
lose the magnet. (Nissan)
Note: Aluminum valve bodies should be
handled very carefully. Do not use bottle
brushes or any cleaning tools in aluminum
valve bodies, as they can scratch the bores.
After the filter has been removed, the valve body bolts
can be unfastened and the valve body can be removed from
the case. As you remove the valve body, carefully note the
position of all valve body parts, including springs, oil feed
tubes, linkage attachments, and check balls, Figure 15-18.
Place the assembled valve body and related parts, as well as
any modulator parts, together in a safe spot on the work-
bench.
The valve body should be thoroughly cleaned in sol-
vent to remove dirt and metal particles. Before cleaning, be
sure to remove any plastic parts or electrical devices that
could be damaged by the solvent.
To repair a sticking valve, remove the valve from the
valve body. Most valves are held in the valve body by small
retainer plates. To avoid mixing up the valves, remove one
retainer plate at a time. Clean and reassemble the valves
under that retainer plate before going on to the next one. If
the retainer plate holds more than one valve, be careful to
return the valves to their original positions.
Sticking valves can sometimes be loosened by lightly
polishing the valve lands with crocus cloth. This is espe-
cially important when polishing aluminum valves. Some
manufacturers recommend using a microfine lapping com-
pound instead of crocus cloth. Always polish in a rotary
motion, or around the surface of the valve lands. Be careful
not to polish the sharp edges of the valve, as these help
keep the valve from jamming on small pieces of dirt. Be
sure to remove all traces of cleaning compound. Cleaning
the valve bore may also restore a valve to proper operation.
If proper operation cannot be restored, the valve or the
valve body assembly must be replaced.
It is not necessary to completely disassemble the valve
body if you just want to check the valves. How ever, if the
transmission is very dirty or sludged up, the entire valve body
must be disassembled. Accumulators must be removed to
clean out sludge and metal particles. Always consult the
service manual for a valve diagram. Figure 15-20 shows the
relative positioning of valves and springs. This illustrates how
these components should be installed in the valve body.
When disassembling the valve body, watch for check balls,
springs, and other small parts that must be reinstalled.
Check the spacer plates for warping, baked-on gasket
material, deep scratches, or pounded out check ball orific-
es. Damaged spacer plates should be replaced.
Also, carefully check the inner manual lever, which
holds the manual valve in position. Check the teeth on the
cockscomb to make sure they are not worn, Figure 15-21.
Check the spring-loaded roller or ball to make sure it puts
pressure on the teeth and holds the lever in position.
Shift Kits
Sometimes, the original transmission or transaxle pres-
sure and oil flow designs are not adequate for older units.
Age and wear often require that the original pressure and oil
flow designs be modified to prevent problems. Many techni-
cians install shift kits, or shift improvement packages, to
improve the operation of a transmission or transaxle. Shift
kits consist of upgraded springs, valves, seals, and other
parts, most of which are installed in the valve body. These
parts modify internal pressures and the fluid flow to improve
shift feel and transmission/transaxle durability. Many shift kits
contain drill bits for enlarging restrictor holes in the spacer
plate. Shift kits always contain instructions for the installation
of the new parts. Sometimes there are instructions for making
modifications to other transmission parts to increase
The valve body casting should be checked for porosity,
cracks, and damaged machined surfaces. Orifices and pas-
sageways must be clean and free from damage. Valves
should be checked for burrs, nicks, and scores. Springs
should be checked for distorted or otherwise damaged
coils, Figure 15-19.
Check all valves for free movement in their bores. Any
valve that does not move freely in its bore is sticking and
can cause problems. Valves can be manually moved in
their bores against spring pressure. If the spring does not
return the valve to its original position, the valve is sticking.
Some valves will not stick until they are removed and rein-
stalled. This is because the valve and bore have worn
matching grooves as the valve moves in the bore. If the
valve cannot be made to move freely, the valve body
should be replaced.