My bike recently started to develop a wobble on the back wheel. I realised that it was due to the bearings failing, so I decided to take it apart and try to fix it. I found another rear wheel that had been bent, so I had some spare parts to use.
Once I pulled the gears off, there was this piece with bearings on it. I counted and there were 88 bearings in total. There are 9 bearings on each side of the axle. There are then 39 bearings around this piece in the picture, and then 31 that go on the gear piece.
The hardest part was making sure that there was the proper amount of bearings in each part. Once I got it all back together, it worked great, and it no longer had the wobble because I replaced the broken part.