It is 18 mm on the newer models. You may have to drop the crossmember and the rear of the trany for good access. I use half inch drive, impact deep socket, hex design, and two 24 inch extensions. Sometimes a good impact wrench will work well. Also have use a long handled breaker bar and braced myself and used my foot (shoe on) to push. I use one bar with a wobble end which seems to work quite well.

Tiz a tough job at times. Once out, make sure you clean bolts and threads so it is easy to reassemble.

Good luck,

dick