Socket size is 22mm. However, my socket was too large when it was on my 1/2 ratchet as it was hitting the heat shield. Switched to a 7/8" socket with a 3/8 ratchet and had no problem. Hope this helps someone else.

 

It sounds like this was mostly about 3/8 drive vs 1/2, rather than 7/8 vs 22mm.

A 1/2 drive needs to handle more torque, thus more bulky socket.

So a 22mm 3/8 probably would have worked also.

What is most important to consider seems to be make sure you got sockets that fit before starting this job.

The adage, always remove fill plug first applies. If you drain, only to find any issue with removing fill, you're stuck. If you can't remove fill, you can delay job until resolved.

 

Both 7/8 and 22mm would have worked with 3/8 but I didn't have a 22mm socket for 3/8 so had to use what I had.