help 308 sprinter shakes in 5th gear on over run?

hi all. my 1998 sprinter shakes on the over run in 5th,ive replaced both front ball joints,drop links,anti roll bar bushes,all new tyres and balanced,changed the prop.if i dont put the van in 5th gear till ian doing 60mph and let of throttle it doesnt do it and you can drive all day fine but if you put it in 5th around 50mph and let of throttle i get the shake as soon as i touch the throttle it goes away it allso goes if i press the cluth so thinking worn clutch anyone else had this.