Just for complete-ness I've done a write-up of the whole saga, and all the steps I did to diagnose, try out, etc, so it might be useful to others for the future. http://www.thebmwz3.co.uk/2017/06/chrysler-grand-voyager-flexplate.html It covers: Balance Shaft Assembly on base of engineAccessory belt removal/replacementOil Sump removedBalance Shaft Assembly removedInjector return leak testFlexplate removal (Separation of the gearbox and the engine)