wade's95chevy

my truck has a 305 which has 267000 miles. the motor is runnin great still but the transmission is whinning. i was told something about a master gear was going out but i have no idea about transmissions. will also grind going into reverse and i was told that this master gear is connected to reverse gear which is causing the grinding. wondering if there is any truth to this and if so what can be done short of rebuilding or buying a new tranny. also the plug hole in the side of the tranny is a 11/16 and i haven't found anything to get it out yet. any kind of help would be appreciated...

ps: truck has 5 speed standard was also told it was the larger trannsmission something like a 400? but idk

97RedBull

every transmission has their ending points and for this one it just might be now because blazers are notorious for going out around 160k and older silverados sometimes a little less than that, just depends on the maintenance and the driver. but 267,000 is a hell of alot on the stockk trans. i think your main drive gear is worne down to the edge of the teeth, they just wear out over time, nothing u can do for that.