What's the 2006 Hyundai Elantra transmission filter location?

You're lucky, in that older Hyundai Elantra's, prior to 2006, usually had the filter in the transmission itself, requiring splitting the case sections to get inside and change it. In Your case, You should find it within the plastic valve body cover on the front. You'll be able to service this by unclipping that and getting to the filter itself. A compatible part here is going to be AutoZone's Duralast Transmission Filter TF96, which runs about $10 in-store, and as You'll see, is juSTSomething You can insert. You'll want to top off the transmission fluid after You replace this, to account for what was saturated within the filter when You changed it out.