[JackM]

Those are just the engagement teeth and will only affect how the tranny feels when the slider happens to butt up against the middle of the tooth that needs to be sharp. If it butts up to the tooth and is unable to 'slip' the slider past, due to missing a sharp edge, you will miss that gear. I would say it is up to you. It looks to me like once every 10th time you try to shift quickly into 3rd you might have an issue, but otherwise it will be okay. Normal driving you wouldn't feel much of a difference at all IMO. I would highly recommend NOT filing them down. If you do that and take too much off you will take away enough of the teeth to give the slider some difficulty in staying engaged to the gear. IOW, it can start popping out of gear. I would either leave it alone or replace the gear with a new one.

Also, if the gear looks that bad, in most cases the slider is worse and considering the slider is doing 2 jobs (operating the synchro ring and engaging the gear) replacing the slider is far more important and you should look into at least do that.

Also, look at the leading and trailing edges of your synchro ring teeth. They look to be worn and compressed a little. This will cause grinding at high RPM as the slider will slip away from the ring too soon (before the gear is synchronized) under high load/stress conditions. I would replace the ring too.

Jack