The transmission filter and fluid should be changed as part of your regular maintenance routine, at least every 30,000 miles.
You will need the following:
1. A filter change kit:
2. A socket set:
3. A drain pan (not pictured)
4. Replacement transmission fluid. The manual suggests a Mercon V type fluid.
Step 1. To begin, put the vehicle up on ramps or raise it with a jack and securely support it on stands.
Step 2. Direct your attention to the transmission drain pan. It is located aft of the oil drain pan underneath the car.
You will have to examine the drain pan to determine which model transmission you have. As you can see, I have the AX4N model. There are several different models on the Gen 3, and they do not have similar gaskets. I do not know if the filters themselves differ from model to model, but the prices are all about the same so make sure you get the right one.
Step 3. Using your 8mm socket, carefully loosen each bolt about 1/4 of a turn all the way around.
Step 4. Remove the bolts on one side of the pan. Fluid will start to drain from the pan. Make sure you have a pan below to catch the falling fluid.
As you remove the bolts, more fluid will start to flow.
Step 5. Once the pan stops draining, remove it completely, and inspect the old filter.
Step 6. Make sure you also remove the filter seal inside the housing. CAREFULLY pry it loose with a pair of needle nose pliers.
Step 7. Examine the empty drain pan.
Step 8. Remove the old gasket.
Step 9. Inspect the magnet. This is designed to catch loose metal through the transmission system.
Step 10. Using a high-flash point solvent (such as brake cleaner or carb. cleaner) clean out the drain pan.
Step 11. Allow to air dry.
NOTE - the drain pan holds about 7-8 quarts of fluid. There's a transmission reservoir that holds another 4-5 quarts. At this point, you could use additional fluid to empty out every last bit of the old fluid. Is this necessary? I personally don't think so. The new fluid combines with the old, and as long as you keep up with the regularly scheduled filter changes you'll have replaced the old fluid over the length of a couple of changes. But what do I know? I've only done this 11 times on the same transmission.
Step 12. Install the new filter. Make sure it fits just as the original did, there are some "sprockets" designed to brace it against the transmission cooling tubes and it must line up.
Step 13. Reinstall the drain pan. Slowly tightening the bolts all the way around. Do not overtighten.
Step 14. Using a funnel, refill the transmission fluid.
I suggest filling with 6 quarts, then going through with the process of checking the fluid, and refilling in increments. You may need as little as 7 quarts, or as much at 8. I believe total system capacity is about 12.5 quarts.
Be sure the properly dispose of the old transmission fluid. DO NOT DUMP IT IN THE WAL-MART PARKING LOT AT 3AM.