Started getting a bad shimmy in the rear end today at about 45, just literally started out of the blue. recently it's gone down to about 35 when it starts. it's not rpm, speed, or throttle related. i'm pretty new to hondas and im not sure what i should be looking for under there. is there anything that typically fails in that system?

 

Is it a shake, wobble, or heavy vibration? Your exhuast may be loose