I have a 2004 S80 that has developed a severe shake and shimmy during acceleration or while under load (maintaining speed)
Tires good
Alignment good
Front end control arms good
Engine good
Transmission good

What could cause this?

 

CV axle

 

The right front side axle goes bad and need to be replaced. Sometimes if it is bad enough the left side goes bad after a while as well but that's rare.