Gearbox contents. Oil or grease?

We are replacing a gearbox. The new gearbox is using oil for lubrication. Is this legal? Or do we need to drain the oil and pack it with grease?

Thanks

There are almost no gearboxes that would put up with being filled with greaseā€¦ especially if its got a high speec shaft gping into it. Get all the teeth coated and no mare than half the airspace.

You need to read the rules carefully! Sealed oil might be ok. Hydraulics ate not.