I always compare the gear wear to the inside most area of the teeth. I noticed some weird gear wear on my small block on this last inspection and when I put it in the block to check how much slop it had it turns out the bushing in the block was shot. It hadn't been in very long but it was very worn so I changed it and put another gear I had in. I have always just dropped the gear in and never checked that bushing, I am glad I noticed it before it chewed up another gear.