Car Repair Help by Professional Mechanics
How Do I Repair My Car? /
How Do I Change
My Transmission Filter?
How to Service an Automatic Transmission
Changing the fluid in the transmission in your vehicle promotes proper operation
and helps the transmission last longer without failure. All car manufacturers have
different service intervals for particular transmission. In a typical transmission
service, the fluid is completely flushed, a filter is changed, the transmission
pan is cleaned and a new pan gasket installed. When refilling, use manufacturer
specified fluids.
READ COMPLETELY BEFORE STARTING!
Step 1 - Replacement Parts (service kit) and Transmission Fluid
Start with proper tools; transmission fluid and transmission filter service kit.
The service kit includes a transmission filter with seal and pan gasket. All transmission
fluid varies from car to car. Consult your vehicle's owner's manual for your particular
type of transmission fluid.
Step 2 - Identify Components
Most automatic transmissions have a service pan that houses the transmission
fluid and filter. This transmission has a heat shield to keep heat from the exhaust
away from the transmission. Some transmission pans have a fluid drain plug used
to drain fluid.
Step 3 - Drain Transmission Fluid
Drain transmission fluid: 1.) Insert drain plug removal tool and turn counter
clockwise. 2.) Loosen the drain plug until easily removed by hand. Some transmissions
do not have a drain plug. In this case the fluid will exit when the transmission
pan is removed.
Step 4 - Drain Transmission Fluid
After the drain plug is loosened, remove plug to drain transmission fluid into
oil catch pan then let drain until completely empty.
Step 5 - Remove Transmission Pan
When the fluid is finished draining, remove transmission pan mounting bolts.
Remove all but two bolts to hold pan in place.
Step 6 - Removing Transmission Pan
When all but two bolts remain, place your hand under the transmission pan and
remove the remaining bolts. Gently lower the pan from the car. You may have
to move a heat shield or gear selector cable mount to remove the pan.
Step 7 - Checking the Pan for Metal Debris
When the fluid pan is removed, inspect the pan for metal debris. All transmissions
have some metal in the pan but excessive metal can mean you may have more serious
problems. The transmission in the diagram is very well maintained and has little
metal in the pan. Most transmission pans have a particle magnet that traps metal
and keeps it away from moving parts.
Step 8 - Clean Transmission Pan
Fit Gasket
Before fitting your new gasket to the transmission pan, clean the pan magnet
completely. Some gaskets are manufactured with gasket sealer built right in like
the one in the diagram above. If your gasket is made of cork or some other style
of gasket, you will need a gasket fastening cement before you can install the gasket.
Step 9 - Changing Transmission Filter
Most automatic transmissions have a filter that is located in the transmission
pan. Some filters are secured to the transmission with bolts or clips. The transmission
filter in this photo is held in by an o-ring seal at the front of the filter. Grasp
the transmission filter firmly and twist slightly to remove, fluid will be present
in the filter.
Step 10 - Identify Internal Transmission Parts
Before reinstalling transmission pan; clean the gasket sealing surface with a
shop towel. This enables a secure seal to the new gasket when the pan is reinstalled.
While the transmission pan is removed you can inspect the electrical connection to
the shift control solenoids. The control solenoids determine what gear the transmission
is operating in and are housed in the valve body. All electrical connectors inside
the transmission should be secure for a good electrical connection.
Step 11 - Re-install New Transmission Filter
Always replace the seal for the transmission filter. As with most seals, it
is important that this seal does not leak. If the transmission filter seal leaks
it can cause the transmission to ingest air causing low transmission hydraulic pressure,
allowing the clutch disc's to slip and cause premature failure. Re-install filter
in its proper location, re-bolt or re-clip as needed.
Step 12 - Re-Install Pan
Carefully reinstall the transmission pan, do not damage the gasket on reassembly
or transmission fluid could leak. Reinstall bolt and tighten them in sequence one
away from the other and continue until all pan bolts are snug. (Note: do not over
tighten, pan gasket could flatten out and leak)
Step 13 - Remove Transmission Fluid Level Check
Locate and remove the transmission fluid level checker, in most cars and trucks
this is where the fluid is checked and added.
Step 14 - Refilling Transmission
Insert fluid funnel and add transmission fluid until the proper amount of fluid
level is reached. Let engine warm and recheck fluid level, add fluid as needed.
Do not over fill the transmission, it could foam the fluid and cause low fluid pressure
causing premature transmission failure. Recheck transmission for leaks and recheck
fluid level in a couple of days.
Common Problems
- Premature transmission failure due to lack of maintenance, low fluid, dirty
filter.
- Manual transmission: premature clutch failure due to abusive driving habits.
How Do I Repair My Car?
/ How Do I Change
My Transmission Filter?
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