AU V8 ute auto have a weird free running vibration mainly on decalleration 1300 to 900 rpm shacks the whole car motor completley rebuilt full balance goes very well. vibration occurs in neutral or drive bad at cruise 60to 70km/h.Idle is slighty rough does feel like a miss just can not pin point which cylinders

Have you tried pulling leads? Could be the converter too. Was it doing this before the rebuild?

Just a thought but when you say "rebuilt full balance" do you mean the balancer itself is new or the motor?
It's just that if it occurs at certain rpm only, a failing balancer can cause such a rough running vibrating effect at certain rpm.

thanks guys yes the engine recond fully and a new balancer install finally found it last night the new balancer not assembled correctly slight out of phase putting all the timing out .Drives like a new one finally Thanks for help