Required tools and materials:
* Set of socket wrenches
* Flat head screwdriver
* Special oil seal remover
* New automatic transmission crankshaft rear oil seal
* Sealant
* New automatic transmission filter
* New automatic transmission oil
Steps to replace the rear crankshaft oil seal of an automatic transmission on a Mazda 3:
1. Precautions:
* Set the vehicle to the parking brake and secure both front wheels with wheel chocks.
* Allow the engine to cool.
* Disconnect the negative terminal of the battery.
2. Draining transmission oil:
* Find the automatic transmission drain plug under the car and place a container under it to collect the oil.
* Carefully unscrew the drain plug and drain all the oil.
3. Removing the automatic transmission:
* Disconnect the gear shift cable from the automatic transmission.
* Disconnect all electrical connectors and vacuum hoses from the automatic transmission.
* Unscrew the bolts securing the automatic transmission to the engine and mounts.
* Carefully lower the automatic transmission and place a support under it so as not to damage it.
4. Removing the old oil seal:
* Locate the rear crankshaft oil seal on the automatic transmission input shaft.
* Using a flathead screwdriver, carefully remove the old oil seal from its socket.
5. Installing a new oil seal:
* Apply a small amount of sealant around the outer edge of the new oil seal.
* Insert the new oil seal into its socket using a special oil seal remover.
* Using a hammer, lightly push the seal into place until it seats in place.
6. Automatic transmission installation:
* Clean the surfaces of the engine and automatic transmission that will be connected.
* Apply a thin layer of sealant to the contact surfaces.
* Carefully align the automatic transmission with the engine and tighten the mounting bolts.
* Connect all electrical connectors and vacuum hoses.
* Attach the shift cable.
7. Filling with transmission oil:
* Find the automatic transmission filler plug and unscrew it.
* Fill the required amount of new transmission oil into the automatic transmission.
* Install a new drain plug and add additional oil until it comes out of the fill hole.
8. Replacing the automatic transmission filter:
* Remove the automatic transmission pan and remove the old filter.
* Install the new filter and secure it with bolts.
9. Final steps:
* Check the transmission oil level and add if necessary.
* Connect the negative terminal of the battery.
* Start the engine and let it idle.
*Change gears to make sure they work properly.
*Check under the car for leaks.
Note: The time required to replace the rear crankshaft oil seal on a Mazda 3 may vary, but it usually takes 3-5 hours to complete the job.