Don’t know what model jack you have. But maybe this information will work for you. It has been a few years since I worked on my H&H Engineering/Barker Mgr. Co jack. So here is their website with link to an Owner’s Manual. (Many models appear to work the same way.)
Here are the instructions that should work with most jacks:
Powerhead must be synchronized with the jack post
1. Use the crank to fully retract post
2. Crank jackpost one turn in opposite direction.
3. ground powerhead to jackpost or trailer frame.
4. Toggle switch down as if lowering the trailer or retracting the post. Continue to hold switch down until motor stops running (as if jackpost is retracted all the way).
5. Install powerhead and tighten (3)set screws.
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 free cover. DO NOT insert screw driver blade! (This may damage mating surfaces.) Before replacing cover, clean mating surfaces. If lubrication is needed, use Lubriplate GR-132 grease or equivalent.
DIVISION OF BARKER MFG. CO. 730 E. MICHIGAN AVE. / P.O. BOX 460 BATTLE CREEK MI 49016 / (269) 965-2371
I phoned them and they were very helpful.