Using the tongue jack has no effect on how hard the bars are to swing back and forth, that is entirely a result of the bolt torque. What the tongue jack WILL do for you is make it to where you do not need a pry bar to lift the bars onto the L brackets on the trailer tongue. On my trailer I can jack up the whole unit and just push the bars sideways onto the L brackets with little to no lifting.
I know you said it's greased, but is it greased correctly? Are the square sockets on the hitch head greased top and bottom or are the bars that go into the sockets greased? The grease has to be on the top and bottom of the square brackets and not on the bars themselves.
If they are already greased I would find someone with a torque wrench that can loosen the bolts and then re-torque to 45-65 lb ft. In fact I would loosen the bolts and swing the bars back and forth a few times to spread the grease out, and then torque to specs. After that they should be a lot easier to swing.
If re-torqueing has no effect then you will have to take the head apart, clean the grease and look for scoring on the sliding surfaces.
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2001 Suburban 4x4. 6.0L, 4.10 3/4 ton **** 2005 Jayco Jay Flight 27BH **** 1986 Coleman Columbia Popup