I recently purchased a 2005 Yamaha bruin 350 4x4, I wasn't too crazy about it only because of the ultramatic transmission with no gears, mainly no low range\granny gear. I've heard though that these quads are a decent all around general purpose atv. Since the day I got it, it's had an intermittent vibration, but only when it's in forward gear and either being accelerated or when the engine is running against the gear, such as going down a steep hill from a higher speed and letting the whole way off the throttle. Sometimes it doesn't vibrate at all, other times it is so bad I have to be really easy on it because I'm worried something is going to come apart. I've jacked up the rear end and started it and put it in gear and revved it up and theres never a noticable vibration or wobble or anything. However, I recently was changing the rear brake shoes and noticed that the wheel bearings have quite a bit of play in them and I could move the axle up and down inside the rear end. I got online within 10 minutes of finding this play and ordered a set of new wheel bearings and seals. I have read numerous forums online that mention how notorious Yamaha quads are for having vibrations, specifically the bruin, moto4, big bear and similar 4x4 utility quads. I've read alot of comments about rear end bearings, this confused me because I thought rear ends only had wheel bearings in them. Where are these rear end bearings located and does anyone know what causes this vibration? The wheel bearing play is the only loose parts I've found. Thank you for any input!