Hi Ian, The speed your gearbox changes up is dependent on a few variables, load, throttle setting, which engine you have etc but for reference I have the 4.2 V8 with the same 6 speed ZF you have and it generally changes up somewhere between 1700 and 2000 revs. ZF recommend a service including oil and filter (which I think is part of the sump) at 100,000 km