How do you add transmission fluid to a 1998 Toyota Avalon?

Answer 1

One adds Transmission Fluid the thru the same tube that the transmission dipstick is in. You will need a funnel that fits into the top of the tube. Pull the transmission dipstick and put in the funnel, then add fluid.
Make sure you don't try mix the oil dipstick with the transmission dipstick!
And, make sure you use the appropriate transmission fluid and do not overfill - read your book!
You can change your fluid at least 3 different ways.
1 (easiest) Remove the plug on the transmission pan located on the driver underside side of the vehicle. (The pan on the passenger side is for the engine oil.) Then as mentioned above, fill the transmission back up thew the same tube as the dipstick is in. The dip stick has 4 notches, you will be filling the trans up to the level in-between the lower two notches as your car will be cold. The dipstick even tells you what kind of transmission fluid to buy. I'd but 5 quarts before starting, but DO NOT OVER FILL.
2 (better) Remove the plug as mention above, then remove the transmission pan. There is a metal filter inside that after removing should be cleaned w/a solvent (gas would work) & blown out. No need to buy a new one as they're designed to last forever. Completely clean off the old gasket before installing the new one on the pan. Refill as mentioned above but DO NOT OVER FILL.
3 (best) Take to a transmission shop, pay about a 100 bucks & have the system flushed. When they do that, they don't even have to pull the pan. They hook up to one of the lines & pump new fluid in while the old fluid comes out. This process gets the 2 or 3 quarts of dirty fluid out of all the lines & torque converter you can't drain. If you're wanting to pay on top of that to clean the filter, expect to pay about another $75.
4 Recheck the fluid level w/the motor running in park w/the emergency back on after a test drive to obtain a accurate level, but DO NOT OVER FILL.