I like #000 grade grease, but as long as you have some sort of oil or grease that flows back in on itself, you will be ok. There is no real high torque or stress in the gear box so all the oil has to do is lubricate the gears and bushings.
Standard grease will not work, after a few turns, the gears have pushed all the grease out to the edges and there it will stay. A #00 or #000 grade grease will flow back in and self level. Penrite, and any gear oil will do the same. John Deere grease is a #00 grade and is a easy to get, cheap priced grease.
If your gear box has good seals and tight bushings, then anything you dump in it will work. Most of use change over to the grease since its much thicker and takes a lot longer to leak out.
Do a search for John Deere corn head grease, or steering box lube, and you will find days and days worth of reading.
Joe
