Continuously Variable Transmission
Description: A Continuously Variable Transmission (CVT)
uses an arrangement of pulleys and bands to achieve an unlimited variation
between the highest and lowest ratios. Unlike conventional automotive
transmissions, CVTs do not employ a graduating arrangement of fixed gear ratios
to deliver power transmission. CVTs have seen spotty vehicle applications over
the years, but have staged a recent comeback due to improving and emerging
technologies.
Purpose: CVTs help the engine stay closer to its most
efficient operating range, which can help both performance and fuel economy.
CVTs may also offer manufacturers different economies of scale for transmission
manufacturing.
Maintenance Tips/Suggestions: CVTs require a different
maintenance regimen than conventional manual or automatic transmissions. Refer
to your car’s owner’s manual for specific recommendations for CVT
maintenance.
Filters
Description: Automatic transmissions/transaxles use a
filter on the inlet side of the transmission’s hydraulic pump. Different types
of filtering media may be used including a fine mesh screen, paper, or felt for
filtering media.
Purpose: A transmission filter prevents harmful
contaminants from entering the hydraulic system, where they can increase wear
and cause scoring and sticking of hydraulic control valves. Additionally, if a
major part fails inside the transmission, the filter may prevent pieces of that
part from contributing to a more catastrophic transmission failure. Normally
transmission filters trap metal chips from hard parts like gears and bushings
and the normal fine material that results from wear of the hydraulic clutch
facings and bands.
Maintenance Tips/Suggestions: Your car’s automatic
transmission filter and fluid should be changed periodically according to the
schedule in your owner’s manual. Although some maintenance schedules may claim
that the transmission fluid or filter doesn’t need to be changed for the life of
the car, remember that the average driving situation falls into the "severe"
maintenance category due to short trips and stop-and-go driving. Some shops
offer transmission flushing and filling, which is intended to remove more
contaminants than simple draining of the transmission. If you decide to have
this service performed, make sure that the transmission pan will be removed in
order to change the filter before refilling it with new fluid. If the filter is
not replaced, contaminants from the old fluid, along with those dislodged during
the flushing process, could impair flow through the filter and lead to
transmission problems.
Torque Converter
Description: The torque converter portion has the ability
to multiply torque from the engine. The impeller (sometimes called the pump) has
specially curved vanes and is driven by the engine's crankshaft. The turbine
also has specially curved vanes and is connected to the input shaft of the
transmission. Adding a third element, the stator (also called the reactor),
gives the assembly the capability it is named for.
The stator has vanes and is mounted on a one-way clutch, to allow it to
freewheel in only one direction. The stator assembly is located between the
impeller and turbine and redirects oil that bounces back off the turbine. The
force of the redirected oil assists in rotating the turbine, resulting in torque
multiplication. When the impeller's speed is high and turbine's speed is low,
torque can be multiplied by as much as 2:1. When the impeller's speed and the
turbine's speed are about the same, torque can be transferred at almost 1:1.
Beginning around 1980, carmakers took the torque converter one step further by
adding a lock-up function. Lock-up converters also contain a friction clutch
that locks the converter impeller to the turbine, usually in higher gears. A
solenoid-controlled oil passage, commanded by the car’s powertain control module
(PCM), locks and unlocks the converter based on driving conditions.
Purpose: The torque converter, connected to the
transmission/transaxle input shaft, connects, multiplies and interrupts the flow
of engine torque into the transmission. The torque converter supplies torque to
the transmission's input shaft in two separate, distinct ways: hydraulic input
and mechanical input (lock-up converters only). Hydraulic input comes from the
torque converter’s turbine and the amount of input torque can vary depending on
the operating conditions within the converter. Mechanical input results when the
lock-up function of the converter engages. The end result is better fuel economy
because all converter slippage is eliminated when the converter locks. The
torque converter also helps to smooth out engine power pulses, as does the
flywheel on a car with a manual transmission.
Maintenance Tips/Suggestions: The torque converter does
not require any regular maintenance or adjustments, but it may be possible to
change the transmission fluid in the converter through draining (if equipped
with a drain) or with a transmission flushing and filling machine. Much of the
transmission’s fluid stays in the converter and since the converter produces a
tremendous amount of heat (the enemy of transmission fluid) there’s good reason
to change it if possible.
Torque converter problems fall into two categories:
1) problems within the torque converter itself, or
2) problems within the torque converter clutch.
If you suspect a problem with the converter or transmission, have it
evaluated by a qualified transmission specialist. With the complexity of today’s
transmissions and torque converters, there’s no room for guesswork.
Flywheel
Description: The flywheel for most automatic
transmissions/transaxles is simply a stamped-steel disc with a ring gear located
at the outer edge for engagement with the starter’s pinion gear. With this type
of flywheel, the torque converter has no ring gear. Some cars use a more modest
flywheel known as a flexplate, which is all that’s needed because the torque
converter itself has a ring gear located on its outer edge.
Purpose: The flywheel, or flexplate, mounts to the
engine's crankshaft and also serves as a mounting location for the torque
converter. Consequently, the flywheel or flexplate transmits engine torque to
the torque converter housing. The flywheel’s ring gear also serves as an
engagement point for the pinion of the starter motor when cranking the engine.
Because of the lightweight design of the flywheel or flexplate, it does not help
to smooth out power pulses from the engine like the flywheel does on a car with
a manual transmission. On cars with automatic transmissions, the torque
converter provides this function.
Maintenance Tips/Suggestions: The flywheel/flexplate does
not require regular maintenance. Sometimes, the ring gear may suffer damage from
improper starter engagement or alignment. If this is the case, the ring gear or
flywheel may need replacement.
Transmission Fluid
Description: Automatic transmission fluid is specially
formulated oil ™ containing numerous additives to withstand gruelling operating
conditions. There are several different types of automatic transmission fluids
and should be used according to the recommendation in your car's owner's manual.
Some examples include:
- DEXRON® III/MERCON® - Recommended for all automatic transmissions requiring
DEXRON® III, DEXRON® IIE, DEXRON® II, DEXRON® or MERCON ® transmission fluids.
It can also be used where fluids meeting Ford ESP-M2C138CJ or Ford M2C166-H
specifications are required.
- ATF+3® -- Formulated exclusively for Chrysler Corp. automatic
transmissions/transaxles where a Chrysler MS-7176, Mopar® or Mopar ATF+3® is
specified.
- Type F (FLM) is a specially compounded fluid meeting the latest Ford
ESW-M2C33F and is compatible with all M2C33 series Ford specifications. In all
1983 and later model Ford automatic transmissions use DEXRON ® III/MERCON ® or
MERCON ® V Automatic Transmission Fluids.
Purpose: Automatic transmission fluid serves a multitude
of purposes. Among other things, it cleans, cools, lubricates, transmits force,
transmits pressure, inhibits varnish build-up and protects the transmission on a
day-to-day basis.
Maintenance Tips/Suggestions: Owner's manual
recommendations on transmission fluid changes vary considerably and may go as
high as 160,000 kilometres or more. For best results, have your car's
transmission fluid and filter changed every two years or 40,000 kilometres.
Always use the type of fluid specified by your car's manufacturer. This
information can be found in the owner's manual or on the end of the transmission
dipstick.
The overwhelming majority of transmission failures are heat-related, and
automatic transmission fluid breaks down rapidly when subjected to high
temperatures. Driving conditions such as trailer towing, quick stops and starts,
ascending and descending mountains, and wheel-spinning in slippery conditions
are but a few scenarios that can devastate the life of the transmission fluid.
Although changing the fluid yourself is not difficult, it's probably best left
to a qualified service technician. This is also a good time to drain the
transmission fluid from the torque converter, if possible. Consult your
technician to see if this can be done.
Gaskets & Sealing
Description: Automatic transmissions/transaxles use an
arrangement of internal seals in clutch packs, servos, and accumulators. There
are also several external seals. These can usually be found where there are any
external linkage connections, where the torque converter engages the oil pump at
the front of the transmission, at the output shaft of the transmission (rear
wheel drive), and at the transaxle drive axle connections (front wheel drive). A
gasket is used between the transmission oil pan and the transmission housing.
Purpose: Internal seals prevent leakage in clutch packs,
servos and accumulators. These components are responsible for applying or
absorbing pressure at various points inside the transmission/transaxle. External
seals prevent the leakage of fluid outside the transmission/transaxle case and
also prevent dirt from entering into the transmission. The oil pan gasket seals
the pan to the transmission/transaxle case.
Maintenance Tips/Suggestions: Symptoms of internal seal
leakage may include slipping, rough shifts, loss of some gear ranges, or no
vehicle movement in forward or reverse. Symptoms of a leaking external seal or
transmission/transaxle oil pan gasket usually can be seen as reddish-brown spots
in your driveway or parking place, a burning oil smell from underneath the car,
and frequent topping-off of the transmission fluid level. If your car shows
signs of seal or gasket problems, have the transmission checked as soon as
possible by a qualified service technician. If the warning signs are neglected,
more serious transmission damage may result.
Transaxle
Description: An aluminium case containing a torque
converter, an arrangement of planetary gears, clutches & bands, servos, a
hydraulic system, solenoids, and a valve body. On front wheel drive cars, the
transmission and differential are combined into a single housing called a
transaxle.
Purpose: An automatic transmission/transaxle changes the
engine’s speed and torque in relation to the speed and torque of the drive
wheels. This keeps the engine’s output matched as close as possible to varying
road speeds and loads. The torque converter, connected to the
transmission/transaxle input shaft, connects, multiplies and interrupts the flow
of engine torque into the transmission.
Maintenance Tips/Suggestions: Most of today’s automatic
transmissions/transaxles do not require any regular adjustments. Check your
owner’s manual to see if any adjustments are required. Owner’s manual
recommendations on transmission fluid changes vary considerably and may go as
high as 160,000 kilometres or more. For best results, have your car’s
transmission fluid and filter changed every two years or 40,000 kilometres.
Fact is, the overwhelming majority of transmission failures are
heat-related, and automatic transmission fluid breaks down rapidly when
subjected to high temperatures. Driving conditions such as trailer towing, quick
stops and starts, ascending and descending mountains, and wheel-spinning in
slippery conditions are but a few scenarios that can devastate the life of the
transmission fluid. Although changing the fluid yourself is not difficult, it is
probably best left to a qualified service technician. This is also a good time
to drain the transmission fluid from the torque converter, if possible. Consult
your technician to see if this can be done.
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