My dryer has developed a vibration. I replaced the rear bearing assembly thinking that might be the problem but the vibration persists. I am pretty sure now that it is coming from the pulley on the idler arm assembly.

What kind of dryer, how old is it, what is the model number.

It is an eight year old Kenmore, model # 970-C82062-10. I was wrong about the idler arm pulley. I replaced it and the vibration persists (after the dryer has been on a minute or two). I now think that it might be the ceramic insulators that hold the heating element. Some of them do not fit tightly into the metal back plate. I talked to an appliance guy at the parts store and he suggested that finding and fixing the vibration might be like trying to fix a rattle in an eight year old car. It might be something I might just have to live with.

He is right. It may be a hard one to find. I have found that the cabinet even flexes enough to give a vibration. You can try putting pressure on different spots when it is vibrating to see if you can quiet it and if so, go from there. Also tipping it slightly in each direction to see if it stops the noise.