hey i stripped my spur gear and replaced it on my 2.5 rusty it took a lil tuning to get the clutch right afterwords and now at top speed when i let off it sounds like its whinning a lil i've torn it apart again to make sure i got it assembled right and it is ... its meshed right not chewing anything up ran like 3 tanks thru it and its fine if i loosen it - it just slips too much if i tighten it - it goes outta control when i let off the gas now i wanna make sure im not going to hurt anything cuz so far no damage from what i can see and i gotta whoop my buddies revo this weekend .... thanx

Gears meshing make noise, you can't get away from that...If it rolls freely and doesn't bind anyplace when you roll the wheels, then I would say it's o.k.