Nissan Navara Vibration

I bought a new spec Nissan Navara in September 2017 at about just after the 15000 km service the vehicle started to vibrate badly at a speed of between 100-120km/h, thinking this was balancing I took the vehicle to Tiger Wheel and tyre in Kempton Park, not resolving the issue I took the vehicle for a second opinion to Tiger Wheel and Tyre in Boksburg where they (Johan) where very helpful in trying to resolve the issue. Not successful I made an appointment with IC Nissan In Kempton Park as this is the closest dealer to me, on the 18 July 2018, disappointing to hear that I have to take the vehicle to the dealer I bought it from which is CMH Nissan Midrand. I phoned Chris the dealer principal at the time and immediately they assisted me. They provided me with a loner vehicle for the period and also could not resolve the vibration immediately. Now this is where the problem starts, they made contact with Nissan SA to assist and from there it is up and down to the dealership to check for possible faults, the vehicle has been back to the dealership a total of 10 times and the issue is not resolved as yet the following was done: Rims and tyres checked and tyres replaced, no improvement Prop shaft changed, no improvement Front discs changed, no improvement Rear drums replaced, no improvement Prop shaft replaced again, no improvement Rear gearbox mount replaced, no improvement When I again phoned Nissan SA on Tuesday 16th, speaking to the lady dealing with the case, Precious Tobakale she told me they got a same spec and model vehicle as mine and they are now going to do back to back tests with the vehicles, I mean What was all the test done up to now? Phoning again yesterday 18th Nissan SA advised that they are talking to the workshop supervisor and the rims and tyres will now be tested. This shows me they dont know what they are doing and playing for time and I have to drive a R 600 000-00 vehicle in this state, am sitting with constant back pain driving this vehicle. Must say CMH Nissan Midrand is doing all they can to assist but unfortunately they have to rely on Nissan SA for assistance

Please I need assistance as what to do next, I am against the wall and it seems Nissan SA does not care