I have a humming noise have have replaced all wheel hubs front to rear.

What is your question?

The car is an Impreza 2006 Automatic.Humming increases with speeds every time you drive the car. As mentioned all wheel hubs were changed but problem wasn't fixed. The car is a front drive with no rear diff and very sluggish on hills or poor in picking up speed.What could be the cause?The car doesnt have leaks and is periodically serviced for engine and gear.

How long has your 2006 Subaru Impreza had this problem?

for like 1 year now