After reading several online posts, and watching several videos, I changed the transmission fluid in my 2016 Sonata Hybrid. This is the procedure I followed.

• Put the front on jack stands and removed both of the bottom shields.
• Loosened the 24mm drain plug.
• Located the fluid level check plug on the front of the transmission.
• Took the car off the jack stands. So it was level.

• Removed the 24mm fill plug on the top back of the transmission.
• Removed the 24mm drain plug and drained the fluid into a catch pan. Was a bit over a gallon. Maybe 4.25 quarts.

• Replaced the drain plug.
• Using an 18" transmission fluid funnel, added 4.5 quarts of genuine Hyundai transmission fluid.
• Replaced the fill plug, and drove the car on the highway for ~20 minutes till I was sure the transmission was hot.

• While still hot, with car level, I removed the fluid level plug with a 3/8 square drive.
• Caught the overflow in a catch pan until it had just about stopped dribbling out.

I'm posting this because a full quart of fluid came out. Meaning I drained 4.25 quarts and refilled 3.5 quarts. I checked the level hot because I read in a few places, and saw on a few videos that the fluid expands when hot and if the level is set cold, it's overfilled. I saw one video that said the car should be running when the level is checked. I did not do this because laying under a hot running car with a fluid plug out seems like a Darwin Award attempt. I searched for why one should have a car running when checking transmission fluid level, and the only thing I could find was that it should be hot, and it gets any trapped air pockets out. Both of these things were accomplished by driving the car till it was hot. I didn't see anything that said that fluid was drawn into part of the transmission when running or anything like that.

I did have a non-Hyundai garage change the transmission fluid not that long ago. I did this change to put in Hyundai fluid because I started to worry about the quality of what they might have used. So unless someone sees something wrong with my procedure I'm going to assume that the garage overfilled the transmission when they changed the fluid.

Thanks,

Gene