Vibration at constant low speed

[JP Desilets]

Hi,

I am an owner of a Toyota Alphard 2005 that I bought a year ago, like it so far but I have an issue when driving at constant low speed between 40 and 80 kilometer an hour. I can feel the vibration on the steering wheel, I brought my van to mechanic expert in import cars, and finally changed tires, new alignment and balancing , changed parts in the front direction, still feel vibration. 

Is someone else had the same problem whit their van Alphard. If you have some recommendations please feel free to get back to me.

Thanks for your support on this issue.

JP