there is a break in period for trannies just like engines. this is all dependent on what was replace when overhauled or if i its all new. trannies have bearings and gears that may have too tight o tolerences and need to "seat" with each other. put in new fluid of the proper weight and viscocity run it or a couple hundred miles and then drain it and check or excessive metal particles i everything looks good replace fluid and go on your way. just make sure to service at regular intervals. but you are going to have people tell you theres no breakin period but their also the ones that say theirs no break in on engines. i guess everyone has there own preferences.
__________________
if you havent been in a small plane its worst, cause your eyes and brain say we are moving and your body says oh no we are not. eyes and brain go asshole we are moving, cant you see? body says fuck you we are not moving at all. so they fight and fight and eventualy your body says, you know what fuck you brain, see if you can stop this!! then you throw up.