You can drive right up to this cache during the day. However, please note that there is a gate a few hundred metres short of the cache that is locked at 5pm. I'm not sure exactly what time it gets unlocked in the morning so I wouldn't try this one too early either - unless you are prepared for a bit of a walk or bike to GZ.
You used to be able to drive (4WD) the Maungatapu Road all then way through to Pelorus Bridge. However, through lack of maintenance, this became an increasing dangerous thing to do and the road was closed to vehicle traffic after a tragic fatal accident in 2009.
You can still walk or bike the road / track to get to places further afield.
That won't be necessary to find this cache though. Park your vehicle, sit down to enjoy the view and find the cache.
Cache is a 200ml Sistema container with log, pencil, eraser and room for small swaps.