This depends on the manufacturer for your jack. What do you have?
My Barker basically says this for maintance:
Once a year, the powerhead should be removed and a
liberal amount of grease (preferably a grease with high
melting point) applied directly to the coupling on which
the drive pin rests.
DO NOT POUR OIL into top of the jack post.
Once a year, the housing cover should be removed and
the gears inspected for proper lubrication.
Remove 4 screws and tap around edge of housing to
DO NOT insert screw driver blade! (This may damage
Before replacing cover, clean mating surfaces.
If lubrication is needed, use Mobilith 460 grease or
DW, 3 Kids and our Goldens
2012 Shamrock 233S
2008 Toyota Sequoia 5.7L 4WD